Does the process of repentance differ significantly based on the sin?

Question

The question How does one repent in Islam? asks about repenting from sins in general. I attempted to answer it, and the general conclusion was basically:

1. Sincerely ask for forgiveness.

2. Perform good deeds to cancel out bad deeds.

3. Manage the worldly consequences.

And, as long as your sincere, that's about it. This question was asked about an unspecified (general) sin.

Question: Does the process of repentance differ significantly based on the sin?

I'm motivated to ask because we get a fair number of "How to repent from X" questions, e.g.: 1. How to repent after breaking a fast by masturbation?, 2. How to repent for apostasy?, 3. How to repent from lying?, 4. How to repent for stealing in my childhood?, 5. How do I repent from swearing by something other than Allah, without knowing it amounts to shirk?. It seems to me that the answer to each one is basically the same.

Answer 1

The process of repentance does not differ significantly based on the sin. There are two aspects to tawba (repentance):

• Methodology
• Conditions.

Both the methodology and the conditions are identical, save for an additional step that is required when tawba is related to a matter that concerns the rights of other people (i.e., managing worldly consequences as you put it in your question).

Methodology of repentance

It is human nature to err and to sin as this hassan (good) hadith says:

عن أنس قال قال رسول الله صلى الله عليه وسلم:‏ كُلُّ بَنِي آدَمَ خَطَّاءٌ وَخَيْرُ الْخَطَّائِينَ التَّوَّابُونَ

It was narrated from Anas that the Messenger of Allah (ﷺ) said: "Every son of Adam commits sin, and the best of those who commit sin are those who repent."

_{— Sunan Ibn Majah, Vol. 5, Book 37, Hadith 4251}

Allah ﷻ informs us in the Qur'an (see 2:222) that He loves those who are constantly repentant, even to the extent that the Prophet ﷺ said that if we were not to sin that Allah would replace us with people who would sin and repent:

عن أبي هريرة قال قال رسول الله صلى الله عليه وسلم: وَالَّذِي نَفْسِي بِيَدِهِ لَوْ لَمْ تُذْنِبُوا لَذَهَبَ اللَّهُ بِكُمْ وَلَجَاءَ بِقَوْمٍ يُذْنِبُونَ فَيَسْتَغْفِرُونَ اللَّهَ فَيَغْفِرُ لَهُمْ

Abu Huraira reported Allah's Messenger (ﷺ) having said: "By Him in Whose Hand is my life, if you were not to commit sin, Allah would sweep you out of existence and He would replace (you by) those people who would commit sin and seek forgiveness from Allah, and He would have pardoned them."

_{— Sahih Muslim, Book 50, Hadith 13}

This is, needless to say, not an invitation for people to sin; rather, it is an acknowledgment from Allah of our weakness as humans and a manifestation of His mercy that He would accept our repentance long as we ask for His forgiveness. To repent, one has to acknowledge that it is mandatory to repent (as no one else will bear the sin or its consequences on one's behalf), fulfill the conditions of repentance and do so in a timely manner (see Islam Q&A's article on repentance).

Repentance from the sin is mandatory. In many verses in the Qur'an, Allah ﷻ commands us to repent sincerely, and we would be forgiven:

يَا أَيُّهَا الَّذِينَ آمَنُوا تُوبُوا إِلَى اللَّهِ تَوْبَةً نَّصُوحًا عَسَىٰ رَبُّكُمْ أَن يُكَفِّرَ عَنكُمْ سَيِّئَاتِكُمْ وَيُدْخِلَكُمْ جَنَّاتٍ تَجْرِي مِن تَحْتِهَا الْأَنْهَارُ يَوْمَ لَا يُخْزِي اللَّهُ النَّبِيَّ وَالَّذِينَ آمَنُوا مَعَهُ ۖ نُورُهُمْ يَسْعَىٰ بَيْنَ أَيْدِيهِمْ وَبِأَيْمَانِهِمْ يَقُولُونَ رَبَّنَا أَتْمِمْ لَنَا نُورَنَا وَاغْفِرْ لَنَا ۖ إِنَّكَ عَلَىٰ كُلِّ شَيْءٍ قَدِيرٌ

O you who have believed, repent to Allah with sincere repentance. Perhaps your Lord will remove from you your misdeeds and admit you into gardens beneath which rivers flow [on] the Day when Allah will not disgrace the Prophet and those who believed with him. Their light will proceed before them and on their right; they will say, "Our Lord, perfect for us our light and forgive us. Indeed, You are over all things competent."

_{— Surat At-Tahrim 66:8}

'Umar ibn al-Khattāb, Mu'ādh ibn Jabal, and Ubay ibn Ka'b (among many others) said that a sincere repentance means one that involves not repeating the same sin again. The Prophet ﷺ iterated the same command through a hadith that further demonstrated that the Prophet ﷺ himself sought repentance a hundred times a day:

عن ابن عمر قال قال رسول الله صلى الله عليه وسلم: يَا أَيُّهَا النَّاسُ تُوبُوا إِلَى اللَّهِ فَإِنِّي أَتُوبُ فِي الْيَوْمِ إِلَيْهِ مِائَةَ مَرَّةٍ

Ibn 'Umar stated that Allah's Messenger (ﷺ) said: "O people, seek repentance from Allah. Verily, I seek repentance from Him a hundred times a day."

_{— Sahih Muslim, Book 48, Hadith 53}

One can seek repentance by asking for forgiveness:

وَيَا قَوْمِ اسْتَغْفِرُوا رَبَّكُمْ ثُمَّ تُوبُوا إِلَيْهِ يُرْسِلِ السَّمَاءَ عَلَيْكُم مِّدْرَارًا وَيَزِدْكُمْ قُوَّةً إِلَىٰ قُوَّتِكُمْ وَلَا تَتَوَلَّوْا مُجْرِمِينَ

And O my people, ask forgiveness of your Lord and then repent to Him. He will send [rain from] the sky upon you in showers and increase you in strength [added] to your strength. And do not turn away, [being] criminals."

_{— Surat Hud 11:52}

قال أبو هريرة سمعت رسول الله صلى الله عليه وسلم يقول: وَاللَّهِ إِنِّي لأَسْتَغْفِرُ اللَّهَ وَأَتُوبُ إِلَيْهِ فِي الْيَوْمِ أَكْثَرَ مِنْ سَبْعِينَ مَرَّةً

Narrated Abu Huraira: I heard Allah's Messenger (ﷺ) saying: "By Allah, I ask for forgiveness from Allah and turn to Him in repentance more than seventy times a day."

_{— Sahih al-Bukhari, Book 80, Hadith 4}

In addition, the Prophet ﷺ said that one may perform wudū' (ablution) followed by praying two rak'ahs (see Islam Q&A's article on the prayer of repentance) as mentioned in this sahih (authentic) hadith in Sunan Abi Dawud:

قال علي رضي الله عنه: كنت رجلا إذا سمعت من رسول الله صلى الله عليه وسلم حديثا نفعني الله منه بما شاء أن ينفعني وإذا حدثني أحد من أصحابه استحلفته فإذا حلف لي صدقته قال وحدثني أبو بكر وصدق أبو بكر - رضي الله عنه - أنه قال سمعت رسول الله صلى الله عليه وسلم يقول مَا مِنْ عَبْدٍ يُذْنِبُ ذَنْبًا فَيُحْسِنُ الطُّهُورَ ثُمَّ يَقُومُ فَيُصَلِّي رَكْعَتَيْنِ ثُمَّ يَسْتَغْفِرُ اللَّهَ إِلاَّ غَفَرَ اللَّهُ لَهُ ثم قرأ هذه الآية وَالَّذِينَ إِذَا فَعَلُوا فَاحِشَةً أَوْ ظَلَمُوا أَنفُسَهُمْ ذَكَرُوا اللَّهَ فَاسْتَغْفَرُوا لِذُنُوبِهِمْ وَمَن يَغْفِرُ الذُّنُوبَ إِلَّا اللَّهُ وَلَمْ يُصِرُّوا عَلَىٰ مَا فَعَلُوا وَهُمْ يَعْلَمُونَ

Ali said: I was a man; when I heard a tradition from the Messenger of Allah (ﷺ), Allah benefited me with it as much as He willed. But when someone of his companions narrated a tradition to me I adjured him. When he took an oath, I testified him. Abu Bakr narrated to me a tradition, and Abu Bakr narrated truthfully. He said: "I heard the apostle of Allah (ﷺ) saying: When a servant (of Allah) commits a sin, and he performs ablution well, and then stands and prays two rak'ahs, and asks pardon of Allah, Allah pardons him. He then recited this verse: 'And those who, when they commit an immorality or wrong themselves [by transgression], remember Allah and seek forgiveness for their sins — and who can forgive sins except Allah? — and [who] do not persist in what they have done while they know.'"

_{— Sunan Abi Dawud, Book 8, Hadith 106}

Repentance should take place right after one realizes that one has committed a sin:

إِنَّمَا التَّوْبَةُ عَلَى اللَّهِ لِلَّذِينَ يَعْمَلُونَ السُّوءَ بِجَهَالَةٍ ثُمَّ يَتُوبُونَ مِن قَرِيبٍ فَأُولَٰئِكَ يَتُوبُ اللَّهُ عَلَيْهِمْ ۗ وَكَانَ اللَّهُ عَلِيمًا حَكِيمًا وَلَيْسَتِ التَّوْبَةُ لِلَّذِينَ يَعْمَلُونَ السَّيِّئَاتِ حَتَّىٰ إِذَا حَضَرَ أَحَدَهُمُ الْمَوْتُ قَالَ إِنِّي تُبْتُ الْآنَ وَلَا الَّذِينَ يَمُوتُونَ وَهُمْ كُفَّارٌ ۚ أُولَٰئِكَ أَعْتَدْنَا لَهُمْ عَذَابًا أَلِيمًا

The repentance accepted by Allah is only for those who do wrong in ignorance [or carelessness] and then repent soon after. It is those to whom Allah will turn in forgiveness, and Allah is ever Knowing and Wise. But repentance is not [accepted] of those who [continue to] do evil deeds up until, when death comes to one of them, he says, "Indeed, I have repented now," or of those who die while they are disbelievers. For them, We have prepared a painful punishment.

_{— Surat An-Nisa 4:17-18}

The phrase "repent soon afterward" in Qur'an 4:17 is interpreted to mean before either of the following time limits is reached (see Islam Q&A's commentary on Qur'an 4:17). This is based on the verse after where it says repentance is not accepted by those who continue to do evil deeds up until their death, then repent when they see the angels of death. This explains why the Pharaoh's repentance was not accepted. The door of repentance remains open for sinners wishing to do tawba until the sinner's death rattle reaches his or her throat or until the sun rises from the west, whichever comes earlier:

عن عبد الله بن عمرو عن النبي صلى الله عليه وسلم قال:‏ إِنَّ اللَّهَ عَزَّ وَجَلَّ لَيَقْبَلُ تَوْبَةَ الْعَبْدِ مَا لَمْ يُغَرْغِرْ

It was narrated from ‘Abdullah bin ‘Amr that the Prophet (ﷺ) said: "Allah accepts the repentance of His slave so long as the death rattle has not yet reached his throat."

_{— Sunan Ibn Majah, Vol. 5, Book 37, Hadith 4253}

عن أبي هريرة قال قال رسول الله صلى الله عليه وسلم: مَنْ تَابَ قَبْلَ أَنْ تَطْلُعَ الشَّمْسُ مِنْ مَغْرِبِهَا تَابَ اللَّهُ عَلَيْهِ

Abu Huraira reported Allah's Messenger (ﷺ) as saying: "He who seeks repentance (from the Lord) before the rising of the sun from the west (before the Day of Resurrection), Allah turns to him with Mercy.‏"

_{— Sahih Muslim, Book 48, Hadith 55}

Conditions of repentance

In Sahih Muslim bi Sharh an-Nawawi 17/25, and in Riyād as-Sālihīn by An-Nawawi, he said in chapter 2 about repentance:

قال العلماء: التوبة واجبة من كل ذنب, فإن كانت المعصية بين العبد وبين الله تعالى لا تتعلق بحق آدمي, فلها ثلاثة شروط

أحدها: أن يقلع عن المعصية

والثاني: أن يندم على فعلها

والثالث: أن يعزم أن لا يعود إليها أبدا

فإن فقد أحد الثلاثة لم تصح توبته

وإن كانت المعصية تتعلق بآدمي فشروطها أربعة: هذه الثلاثة وأن يبرأ من حق صاحبها فإن كانت مالا أو نحوه رده إليه وإن كانت حد قذف ونحوه مكنه منه أو طلب عفوه وإن كانت غيبة استحله منها

_{NOTE. My own translation, so treat with care.}

Scholars say that repentance from every sin is mandatory. If the sin is between the servant and Allah ﷻ and does not pertain to the rights of another human being, repentance has three conditions:

1. To abstain from performing the sin
2. To regret doing the sin
3. To resolve not to repeat the same sin.

If any of the three conditions are not fulfilled, repentance is not valid.

If the sin concerns the right of another human being, the conditions are four: the three previous ones in addition to restoring the right to its rightful owner. If it is monetary, return the money; if is slander, enable the person to carry out its hadd (punishment) or ask for the person's forgiveness; and if it is backbiting, ask the person for redemption.

_{— Riyād as-Sālihīn, pp. 33-34 (Arabic only)}

It is said that 'Abdullah ibn Mas'ūd said that the companions asked the Prophet ﷺ about how to repent from sin as the Israelites used to have their expiation (e.g., to cut their noses or ears) written on their houses' doors. The Prophet ﷺ did not answer, then the following verse was revealed:

وَالَّذِينَ إِذَا فَعَلُوا فَاحِشَةً أَوْ ظَلَمُوا أَنفُسَهُمْ ذَكَرُوا اللَّهَ فَاسْتَغْفَرُوا لِذُنُوبِهِمْ وَمَن يَغْفِرُ الذُّنُوبَ إِلَّا اللَّهُ وَلَمْ يُصِرُّوا عَلَىٰ مَا فَعَلُوا وَهُمْ يَعْلَمُونَ

And those who, when they commit an immorality or wrong themselves [by transgression], remember Allah and seek forgiveness for their sins — and who can forgive sins except Allah? — and [who] do not persist in what they have done while they know.

_{— Surat Āl 'Imrān 3:135}

Ismā'īl ibn 'Abdur-Rahmān as-Suddi said that the phrase "do not persist" means to refrain from asking for forgiveness as per the hassan hadith in Jami' at-Tirmidhi 48/190. Makhūl ibn Abi Muslim, who was one of the major tabi'īn (the generation of Muslims born after the passing of the Prophet ﷺ but who were contemporaries of the companions), said the person who asked for forgiveness most was Abu Hurairah.

In Rawdat at-Tālibīn 11/249 (Arabic only), An-Nawawi said that abstinence from a sin is a requirement for tawba. Repentance from a sin, while the sinner continues to do another sin, does not invalidate the repentance, and if abstinence is intended but not observed then the repentance is incomplete.

The Prophet ﷺ used regret and repentance as synonyms as shown in this hassan hadith in Sunan Ibn Majah (declared as sahih by Muhammad Nasiruddin al-Albani in his book Sahih Ibn Mājah):

عن ابن معقل قال دخلت مع أبي على عبد الله فسمعته يقول قال رسول الله صلى الله عليه وسلم: النَّدَمُ تَوْبَةٌ

It was narrated that Ibn Ma'qil said: "I entered with my father upon ‘Abdullah, and I heard him say: ‘The Messenger of Allah (ﷺ) said: "Regret is repentance."

_{— Sunan Ibn Majah, Vol. 5, Book 37, Hadith 4252}

Regret is the cornerstone of repentance, to the extent that Ibn Hajar al-Asqalani in his book Fat'h Al-Bari 13/471 said that some scholars say the hadith means the origin of repentance is regret and that abstinence from a sin and resolution not to repeat it just follow as consequences of regret. A number of scholars directly related regret over a sin to the sincerity of repentance (see IslamWeb's articles on practical steps towards sincere repentance and how to attain sincere repentance).

An-Nawawi has a chapter about how repentance may be accepted even if one repeats the same sin based on the following hadith in both Sahih al-Bukhari and Sahih Muslim:

سمعت أبا هريرة قال سمعت النبي صلى الله عليه وسلم قال: إِنَّ عَبْدًا أَصَابَ ذَنْبًا ـ وَرُبَّمَا قَالَ أَذْنَبَ ذَنْبًا ـ فَقَالَ رَبِّ أَذْنَبْتُ ـ وَرُبَّمَا قَالَ أَصَبْتُ ـ فَاغْفِرْ لِي فَقَالَ رَبُّهُ أَعَلِمَ عَبْدِي أَنَّ لَهُ رَبًّا يَغْفِرُ الذَّنْبَ وَيَأْخُذُ بِهِ غَفَرْتُ لِعَبْدِي‏.‏ ثُمَّ مَكَثَ مَا شَاءَ اللَّهُ، ثُمَّ أَصَابَ ذَنْبًا أَوْ أَذْنَبَ ذَنْبًا، فَقَالَ رَبِّ أَذْنَبْتُ ـ أَوْ أَصَبْتُ ـ آخَرَ فَاغْفِرْهُ‏.‏ فَقَالَ أَعَلِمَ عَبْدِي أَنَّ لَهُ رَبًّا يَغْفِرُ الذَّنْبَ وَيَأْخُذُ بِهِ غَفَرْتُ لِعَبْدِي، ثُمَّ مَكَثَ مَا شَاءَ اللَّهُ ثُمَّ أَذْنَبَ ذَنْبًا ـ وَرُبَّمَا قَالَ أَصَابَ ذَنْبًا ـ قَالَ قَالَ رَبِّ أَصَبْتُ ـ أَوْ أَذْنَبْتُ ـ آخَرَ فَاغْفِرْهُ لِي‏.‏ فَقَالَ أَعَلِمَ عَبْدِي أَنَّ لَهُ رَبًّا يَغْفِرُ الذَّنْبَ وَيَأْخُذُ بِهِ غَفَرْتُ لِعَبْدِي ـ ثَلاَثًا ـ فَلْيَعْمَلْ مَا شَاءَ

Narrated Abu Huraira: I heard the Prophet (ﷺ) saying, "If somebody commits a sin and then says, 'O my Lord! I have sinned, please forgive me!' and his Lord says, 'My slave has known that he has a Lord who forgives sins and punishes for it, I, therefore, have forgiven my slave (his sins).' Then he remains without committing any sin for a while and then again commits another sin and says, 'O my Lord, I have committed another sin, please forgive me,' and Allah says, 'My slave has known that he has a Lord who forgives sins and punishes for it, I, therefore, have forgiven my slave (his sin). Then he remains without Committing any another sin for a while and then commits another sin (for the third time) and says, 'O my Lord, I have committed another sin, please forgive me,' and Allah says, 'My slave has known that he has a Lord Who forgives sins and punishes for it I, therefore, have forgiven My slave (his sin), he can do whatever he likes."

_{— Sahih al-Bukhari, Book 97, Hadith 132}

An-Nawawi commented in his Sharh 17/75 that even if one commits the same sin more than once, a hundred times, a thousand times, or even more, then one repents each time or repented once collectively that one's repentance would be valid.

Ibn Rajab in Jāmi' al-'Ulūm wa al-Hikam 3/486 quoted 'Umar ibn 'Abdul-'Aziz saying:

أيها الناس من ألم بذنب فليستغفر الله وليتب، فإن عاد فليستغفر الله وليتب، فإن عاد فليستغفر وليتب، فإنما هي خطايا مطوَّقة في أعناق الرجال، وإن الهلاك في الإصرار عليها

_{NOTE. My own translation, so treat with care.}

O people, whoever sins must seek forgiveness from Allah and repent; and if he returns [to the same sine], he must seek forgiveness from Allah and repent; and if he returns [to the same sine], he must seek forgiveness from Allah and repent. It is but sins that wrap around men's necks, and destruction is in their persistence.

While repeating the sin and the repentance of that sin does not invalidate the repentance, one should always resolve not to repeat the same sin in the future. Allah ﷻ informs us that He forgives whoever repents then continues to be rightly guided:

وَإِنِّي لَغَفَّارٌ لِّمَن تَابَ وَآمَنَ وَعَمِلَ صَالِحًا ثُمَّ اهْتَدَىٰ

But indeed, I am the Perpetual Forgiver of whoever repents and believes and does righteousness and then continues in guidance.

_{— Surat Taha 20:82}

If the sin in question concerns the right of another person, restoring this right to its rightful owner is a cornerstone of repentance. If the right cannot be restored (e.g., stolen money returned to its owner), then the sinner has to enable the person to carry out the hadd (punishment) or ask for the person's forgiveness. If the right is not restored during the sinner's life, assuming that the sinner sincerely tried to restore it, then it is hoped that Allah ﷻ would forgive him based on the following hadith:

عن أبي هريرة رضي الله عنه عن النبي صلى الله عليه وسلم قال: مَنْ أَخَذَ أَمْوَالَ النَّاسِ يُرِيدُ أَدَاءَهَا أَدَّى اللَّهُ عَنْهُ، وَمَنْ أَخَذَ يُرِيدُ إِتْلاَفَهَا أَتْلَفَهُ اللَّهُ

Narrated Abu Huraira: The Prophet (ﷺ) said, "Whoever takes the money of the people with the intention of repaying it, Allah will repay it on his behalf, and whoever takes it in order to spoil it, then Allah will spoil him."

_{— Sahih al-Bukhari, Book 43, Hadith 3}

If the sinner cannot restore the right due to the rightful owner being dead, unknown, or otherwise not reachable, then one has to dispose of the unrightful possession (see Islam Q&A's article on rulings on disposing of harām wealth after repentance).

Acceptance of repentance

In many verses and hadiths, we are told about Allah's joy with a servant of His who repents after committing a sin:

عن أنس رضي الله عنه قال قال رسول الله صلى الله عليه وسلم: اللَّهُ أَفْرَحُ بِتَوْبَةِ عَبْدِهِ مِنْ أَحَدِكُمْ سَقَطَ عَلَى بَعِيرِهِ، وَقَدْ أَضَلَّهُ فِي أَرْضِ فَلاَةٍ

Narrated Anas bin Malik: Allah's Messenger (ﷺ) said, "Allah is more pleased with the repentance of His slave than anyone of you is pleased with finding his camel which he had lost in the desert."

_{— Sahih al-Bukhari, Book 80, Hadith 6}

One should always repent while believing that a sincere repentance is always accepted by Allah (see Islam Q&A's article on acceptance of repentance, and IslamWeb's article on how one can know that Allah has accepted one's repentance).

Answer 2

This is a very important question; tawba or repentance is central in Islam. Although you are correct in that the steps of tawba are the same for all sins, there are specific acts of expiation for certain sins that must be done as a part of repentance. I would put these in the subcategory of "managing the circumstances", so the same steps are applicable, but because of the added specific expiations, one could say these sins are treated differently from the rest.

In addition, not all that which people think of as sins are in fact sins for which they are held responsible, as in the question regarding stealing in childhood. Children are not considered like adults in having the level of responsibility to require tawba or repentance. And when that child becomes an adult, s/he is not held accountable for what they did as a child and no repentance is necessary; only if that same person continues stealing as an adult does it require repentance.

Perhaps the most complicated issues arise in the case of murder or manslaughter, where one of those consequences to be dealt with is the pain caused to relatives of the victim, and in the case of believing victims, their value to the Muslim community. In the case of accidental death, the Quran specifies what needs to be done:

And never is it for a believer to kill a believer except by mistake. And whoever kills a believer by mistake - then the freeing of a believing slave and a compensation payment presented to the deceased's family [is required] unless they give [up their right as] charity. But if the deceased was from a people at war with you and he was a believer - then [only] the freeing of a believing slave; and if he was from a people with whom you have a treaty - then a compensation payment presented to his family and the freeing of a believing slave. And whoever does not find [one or cannot afford to buy one] - then [instead], a fast for two months consecutively, [seeking] acceptance of repentance from Allah. And Allah is ever Knowing and Wise. (Surat al-Nisa' 4:92)

This aya shows us specific steps that must be taken to expiate this sin, and this expiation here is part of the repentance; the intention here is "[seeking] acceptance of repentance from Allah." So even though intention and sincerity and reforming behavior is part of the repentance, this case of manslaughter is different in its expiation requirements from other sins.

The very next aya brings up another issue here: are there sins for which no repentance can be accepted?

But whoever kills a believer intentionally - his recompense is Hell, wherein he will abide eternally, and Allah has become angry with him and has cursed him and has prepared for him a great punishment. (Surat Al-Nisa' 4:93)

Because the previous aya shows a way of repentance for manslaughter, the judgment for intentional murder of a Muslim stands in sharp contrast without any discussion of a path of repentance. Of course, it is known that some of the kuffar or disbelievers who were fighting Prophet Mohammad, such as Umar ibn Al-Khattab, killed believers intentionally, and then surrendered to Islam and became Muslim and repented, and their repentance was accepted by Allah. In that case, the killing of believers was an act committed as a part of their disbelief and being among those who were enemies of Prophet Mohammad and his followers. Therefore, in that case the killing is considered part of the kufr or disbelief/ enmity, and the path of repentance for them would be the same as repentance from all kufr. Once the newly-converted Muslim joined the believers, he may expiate his sins in the way prescribed for manslaughter, because his intention to kill existed only in his prior state of kufr from which, after repenting, he has been absolved.

That leaves the Muslim who intentionally kills another Muslim. According to the aya above, he is condemned to hell, which implies he might be considered a kaffir or disbeliever, no longer a Muslim, by committing that act. That would be presuming he has no possible "right" against his victim, as in the case of self-defense or if that person had committed a crime against him or his family or had oppressed him or his family in some serious way.

If in fact the murder was unjust (without rights mentioned above), The murderer's only path of repentance would be to first be expelled from the Muslim community and considered a disbeliever, non-Muslim. (The ramifications of this for terrorism against Muslims are huge.) Then, should he sincerely want to become Muslim again, there is a possible path but it is more difficult.

The aya below refers to the Jews but could apply to anyone who has committed grave sins such as killing a Muslim or those sins mentioned:

And [We cursed them] for their breaking of the covenant and their disbelief in the signs of Allah and their killing of the prophets without right and their saying, "Our hearts are wrapped". Rather, Allah has sealed them because of their disbelief, so they believe not, except for a few. (Surat Al-Nisa' 4:155)

This shows that if a person who is Muslim, and faith is in a sense a covenant with Allah, becomes a disbeliever by either his/her heart or deeds (as per the murder example above), it is possible that Allah could seal his/her heart from faith, which should be a warning about the potential difficulty of repentance for killing a Muslim. Here it is the depth of their remorse and desire for Allah's acceptance and willingness to make sacrifices and do righteous deeds that would make the difference, and be the key to repentance. But one cannot do this repeatedly.

From Surat Al-Nisa' 4:137:

Indeed, those who have believed then disbelieved, then believed, then disbelieved, and then increased in disbelief - never will Allah forgive them, nor will He guide them to a way.

So repentance for the murder of a Muslim and also for disbelief is different from other sins in that one is in a greater "danger zone" of losing one's path to repentance; it has to be taken with the utmost seriousness and fear of Allah's wrath.

Another example of a specific and different expiation for a sin is in the matter of making oaths, from Surat Al-Ma'ida 5:89:

Allah will not impose blame upon you for what is meaningless in your oaths, but He will impose blame upon you for [breaking] what you intended of oaths. So its expiation is the feeding of ten needy people from the best of that which you feed your [own] families or clothing them or the freeing of a slave. But whoever cannot find [or afford it] - then a fast of three days [is required]. That is the expiation for oaths when you have sworn. But guard your oaths. Thus does Allah make clear to you His verses that you may be grateful.

Another example of specific expiations is the case of killing an animal while in the state of ihram during the Hajj in Surat Al-Ma'ida 5:85:

O you who have believed, do not kill game while you are in the state of ihram. And whoever of you kills it intentionally - the penalty is an equivalent from sacrificial animals to what he killed, as judged by two just men among you as an offering [to Allah] delivered to the Ka'bah, or an expiation: the feeding of needy people or the equivalent of that in fasting, that he may taste the consequence of his deed. Allah has pardoned what is past; but whoever returns [to violation], then Allah will take retribution from him. And Allah is Exalted in Might and Owner of Retribution.

Other sins are given specific punishments; those punishments in turn "expiate" the sin, often providing compensation for the victim, and again in that case "managing the circumstances" that arose from that sin. An example of those is for theft, the cutting of hands. However, that punishment only applies to cases where the theft was of something they (the perpetrator) didn't need; theft by someone hungry or in dire need of something for survival of himself or his family is not punishable by cutting of hands at all, and its repentance is only asking Allah's forgiveness and refraining from stealing for any reason other than necessity.

Relevant to that point is that some punishments were given in the Torah, and then either not mentioned in the Quran or mentioned in the context of a lighter sentence or possible mitigated treatment.

As in Surat Al-Ma'ida 5:45 referring to the Torah:

And We ordained for them therein a life for a life, an eye for an eye, a nose for a nose, an ear for an ear, a tooth for a tooth, and for wounds is legal retribution. But whoever gives [up his right as] charity, it is an expiation for him. And whoever does not judge by what Allah has revealed - then it is those who are the wrongdoers.

So if the victim wishes, he can "forgive" (in the sense of giving up right of retribution) the perpetrator and thus remove the punishment. But that is only between perpetrator and victim. Repentance is between the sinner and Allah and the basic rules and conditions of tawba apply.

Those rules for repentance then I would state slightly differently: 1. Admit the immorality/ sinfulness of one's sin -- accepting blame. 2. Sincerely desire, seek and ask Allah's forgiveness and acceptance. 3. Stop committing the sin for which one is repenting and do not come back to it. 4. Expiation (kaffara) for one's sin if specified or by punishment if specified. 5. Do good deeds to compensate for one's bad deed(s).

In the case of conversion to Islam, which is both the biggest (repenting from the worst sin of kufr) and most rewarded and desirable of repentances, Allah will change all one's sins to good deeds.

From Al-Furqan 25:70, referring to the punishment of hell for disbelievers, idolaters, those who kill without rights (prohibited killing), or who engage in adultery (for married or unmarried), gives this opening to repentance:

Except for those who repent, believe and do righteous work. For them Allah will replace their evil deeds with good. And ever is Allah Forgiving and Merciful.

Finally, repentance itself is a righteous act, and Allah repeatedly recommends it and includes it in the list of righteous deeds that define those whom Allah accepts:

[Such believers are] the repentant, the worshippers, the praisers [of Allah], the travelers [for His cause], those who bow and prostrate [in prayer], those who enjoin what is right and forbid what is wrong, and those who observe the limits [set by] Allah. And give good tidings to the believers. (Surat Al-Tawba 9:112)

Answer 3

Yes it's different

It's about undoing wrong things before Allah, yourself and his creation—as much as you can with the highest possible level of presence of your heart. So the more damage one has done the more he has to undo. For example if one has mistreated his parents, then he must undo it by showering them with love. If one has lied about a person then he must tell the truth about that person to everyone. If one has been jealous of another, then he must give them gifts, pray for them so that his heart is turned soft for them. You get the idea...