Is tattooing (Permanent & temporary) permissible in Islam? If a person who wishes to revert to Islam has a permanent tattoo, should he remove it?
The Prophet May peace and Blessings be upon Him Said
Narrated Abu Huraira:
The Prophet said, "The effect of an evil eye is a fact." And he prohibited tattooing.
حَدَّثَنَا إِسْحَاقُ بْنُ نَصْرٍ، حَدَّثَنَا عَبْدُ الرَّزَّاقِ، عَنْ مَعْمَرٍ، عَنْ هَمَّامٍ، عَنْ أَبِي هُرَيْرَةَ ـ رضى الله عنه ـ عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ " الْعَيْنُ حَقٌّ ". وَنَهَى عَنِ الْوَشْمِ.
The prophet may peace and blessings be Upon Him prohibited it in the above hadith, He also said that Allah cursed the one who tattoos oneself or others:
Narrated Ibn `Umar:
Allah's Apostle said, "Allah has cursed such a lady as lengthens (her or someone else's) hair artificially or gets it lengthened, and also a lady who tattoos (herself or someone else) or gets herself tattooed.
حَدَّثَنِي مُحَمَّدُ بْنُ مُقَاتِلٍ، أَخْبَرَنَا عَبْدُ اللَّهِ، أَخْبَرَنَا عُبَيْدُ اللَّهِ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ ـ رضى الله عنهما ـ أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ " لَعَنَ اللَّهُ الْوَاصِلَةَ وَالْمُسْتَوْصِلَةَ، وَالْوَاشِمَةَ وَالْمُسْتَوْشِمَةَ ". قَالَ نَافِعٌ الْوَشْمُ فِي اللِّثَةِ.
It was narrated that Abu Juhayfah (may Allah be pleased with him) said: “The Prophet (peace and blessings of Allah be upon him) cursed the one who does tattoos, the one who has a tattoo done, the one who consumes riba (usury or interest) and the one who pays it, and he forbade the price of a dog and the earnings of a prostitute, and he cursed the image-makers.” (Narrated by al-Bukhaari, 5032).
You do not have to remove a tattoo to become Muslim, becoming Muslim erases all sins of the past. Allah says in Surat 25 Ayah 70 :
إِلَّا مَن تَابَ وَءَامَنَ وَعَمِلَ عَمَلاً۬ صَـٰلِحً۬ا فَأُوْلَـٰٓٮِٕكَ يُبَدِّلُ ٱللَّهُ سَيِّـَٔاتِهِمۡ حَسَنَـٰتٍ۬ۗ وَكَانَ ٱللَّهُ غَفُورً۬ا رَّحِيمً۬ا (٧٠)
Unless he repents, believes, and works righteous deeds, for Allah will change the evil of such persons into good and Allah is Oft-Forgiving, Most Merciful (70)
If someone says that you can not become a Muslim than he/she has wronged, that would be preventing someone from entering Islam, and Islam is for everyone. If someone has a tattoo and was not Muslim than they got it out of lack of knowledge and has nothing to do with entering Islam. It is only after you have become Muslim and gained the knowledge that you are accountable.
According to Wikipedia:
Tattoos are considered forbidden in Sunni Islam, but are permissible in Shia Islam (especially the kind of tattoo which is done on eyebrow). According to the book of Sunni traditions, Sahih Bukhari, "The Prophet forbade [...] mutilation (or maiming) of bodies." Several Sunni Muslim scholars believe tattooing is a sin because it involves changing the creation of God (Surah 4 Verse 117-120). There is, however, difference of scholarly Sunni Muslim opinion as to the reason why tattoos are forbidden.
Using everything which does harm to one's body is not permitted in Islam (haraam or makrooh). While tattoo is inserting needle and ink into the body, it does more harm than good. This is the general statement:
لا ضرر و لا ضرار فی الاسلام
No harm in Islam