I said “Alhamdullilah” out loud during khutba?

Question

The imam said something that really struck my heart and I said "alhamdulillah" pretty loud.

Was this haram?

Answer 1

What one should do while the Imam or Khateeb is holding the sermon of Jumu'ah

Let me first point at a couple of ahadith teaching us the correct virtuous of listening to the jumu'ah sermon:

One should avoid speaking even if it is for the purpose of enjoining what is good and forbidding what is evil, because of:

• 'If you say to your companion: Listen attentively on a Friday when the Imam is delivering the khutbah, then you have engaged in idle talk.'
  (Al-Muwatta', sahih al-Bukhari, sahih Muslim 1 & 2, sunan an-Nasa'i 1 & 2 and sunan ibn Majah all on the authority of abu Hurairah)
• "Whoever said: 'Be quiet' while the Imam is giving the Khutbah then he has committed Laghw (useless activity)."
  (Jami' at-Trimidhi and a similar narration in sunan an-Nasa'i and a much longer in sunan abi Dawood)

Also read this hadith from sunan ibn Majah. And an other about the importance of listening to the khutba in sahih Muslim, sunan abi Dawood and sahih al-Bukhari.

One should listen to the sermon and shouldn't disturb himself nor others:

• on a Friday. A man came and stepped over the people. 'Abd Allah b. Busr said: A man came and stepped over the people while the Prophet (ﷺ) was giving the sermon on Friday. The Prophet (ﷺ) said: Sit down, you have annoyed (the people). (sunan abi Dawood)
• He who performed ablution well, then came to Friday prayer, listened (to the sermon), kept silence all (his sins) between that time and the next Friday would be forgiven with three days extra, and he who touched pebbles caused an interruption.
  (Sahih Muslim, sunan ibn Majah 1 & 2, Jami' at-Tirmidhi, sunan abi Dawood)

Note that this means you may not get the full rewards of this actual jumu'ah prayer if you did something like described, but your prayer will still be valid.

But nevertheless it is allowed to give signs instead of speaking due to:

• The Prophet (ﷺ) used to make a sign during prayer. (sunan abi Daowd)

It is also allowed to do some "action": like waking up somebody whom started sleeping during the khutba (instead of speaking to him to wake him up).

An other evidence used for the importance of listening, following and focusing on the sermon of the Friday prayer is the verse:

So when the Qur'an is recited, then listen to it and pay attention that you may receive mercy. (7:204)

Ibn Kathir in his tafsir quoted from ibn Jarir at-Tabri's tafsir:

Ibn Jarir reported that Ibn Mas`ud said; "We would give Salams to each other during Salah. So the Ayah of Qur'an was revealed; (When the Qur'an is recited, then listen to it.) (source: qtafsir)

As almost all madhhabs consider quoting from the quran and/or sunnah as an essential (or important) part of the khutba!

An other verse is the verse from surat al-Jumu'ah:

O you who have believed, when [the adhan] is called for the prayer on the day of Jumu'ah [Friday], then proceed to the remembrance of Allah and leave trade. That is better for you, if you only knew. (62:9)

but one may say that it is more general, but one could conclude that one should leave all worldly matters when joining the prayer and listening to the khutba (the remembrance of Allah).

Also read What are we recommended to do or frowned upon on Friday's according the Qur'an and Sunnah?

Conclusion 1: To sum up during the Khutba one should avoid anything that may disturb or hinder you or others from following and listening to the words of the sermon one should instead try to focus and follow the words, understand and reflect them ... this might be the central goal of all these narrations and related verses of the quran.

I'd like to point at an other post before Making Dua in middle of salah?

Many scholars made an analogy between the Sermon and the prayer, as people should listen and follow to the sermon, the same as they listen and follow the recitation of the Imam and his prayer. As we know that interaction with tzhe recitation (while listening or reciting) is a good deed (see the link above) saying alhhamdullilah actually Shows that you were following and focussing on the khutba and therefore shouldn't be an act going against the order of listening which I will discuss later.

Conclusion 2: Interaction with the khutba is a recommended act and shows that you are following it and focussing on it.

Fiqh perspective

1. Is listening to the khutba an order or a recommendation?

Imam an-Nawawi in his commentary on sahih Muslim, Aabadi in his 'awn al-Ma'abod (commentary on sunan abi Dawood) quoted the following:

واختلف العلماء في الكلام هل هو حرام أو مكروه كراهة تنزيه؟ وهما قولان للشافعي ، قال القاضي : قال مالك وأبو حنيفة والشافعي وعامة العلماء : يجب الإنصات للخطبة ، وحكي عن النخعي والشعبي وبعض السلف : أنه لا يجب إلا إذا تلا فيها القرآن . قال : واختلفوا إذا لم يسمع الإمام هل يلزمه الإنصات كما لو سمعه ؟ فقال الجمهور : يلزمه ، وقال النخعي وأحمد وأحد قولي الشافعي : لا يلزمه .

Which means:
The shcolars hold different opinions on speaking during the khutba, whether it is haram or frowned upon? Imam a-Shafi'i Held both opinions. al-Qadi ('Iyad?) said: Malik, Abu Hanifa and a-Shafi'i and most scholars said: One is asked to listen to the Khutba (wajib), And it was passed on that an_Nakha'i, a-Sha'abi and other salaf said it is not wajib unless there's a qur'an recitation during the khutba. They also differed about a Person whom doesn't actually hear the Imam, whether he should or not listen as if he was Hearing the Sermon? The majority said he must, while an_Nakha'i, Ahmad and one of two opinions of a-Shafi'i is no he must not!

2. What if you said something out of an emotion or even cried unintentionally?

The jumu'ah prayer is valid, as unintentional acts don't count and the fact that you said "Alhamdulillah" also actually shows that you might be following the sermon.

"Allah has forgiven my nation for mistakes and forgetfulness, and what they are forced to do." (sunan ibn Majah)

Some references:
islamqa #45651
islamqa #89575

Answer 2

In my humble opinion you did nothing wrong, rather I would appreciate that you were so deeply involved in listening to ‘khutaba’ that you responded involuntarily and instantly and it was the voice of your heart. You have praised Almighty Allaah, you will be rewarded, in-sha-Allaah. My arguments regarding this are as follows;

It is recommended that whenever a person passes by a quranic verse (no matter reciting himself or listening while in prayers or in ‘khutaba’ or otherwise) that is about ‘Blessings of Allaah’ he should ask (pray) for it, and whenever he passes by a verse about ‘Hell fire’ he should ask for Allaah’s refuge from Hell fire, and whenever he passes by a verse regarding ‘Punishment’ he should repent.

Ibn Abbas RA narrated in a hadith reported in Muslim that one night he prayed with the Prophet SWS , whenever he recited a verse about ‘Tasbeeh’ the Prophet kept on saying ‘Tasbeeh’, and whenever there was verse about seeking refuge from the evil and the bad he would repent and seek Allaah’s refuge and forgiveness Similarly, there is a hadith narrated by Abu Hurairah RA, the Prophet SWS said; “when one of you recites Surah At-Teen and reaches the last verse he should respond to it by saying ‘Yes! I am of those who bear witness to it’. (Reported by Ahmad, Tirmidhi, Abu Daud, Baihaqi, Hakim, Ibn Al Mundhir and Ibn Marduyah.

Similarly there are narrations in which it is said who so ever reads (La Uqsimu Biyawmi Al qiyama) [Surat 75:40] and finishes its last verse, he should say: "Yes. Indeed". And whoever reads (Al Murslat,Surat 77] and reaches the end of its last verse he should say: "I believe in Allah".

Whenever any body glorify Allaah, Allaah glorify him in much better style and at much better place. Allaah humma tajulnah min hum.

Answer 3

Those who attend the Friday prayer should be silent and listen attentively to the Imam when he is preaching. It is not permissible to speak to others, even if that is to tell them to be quiet.

It was narrated from 'Abdullah bin Ibrahim bin Qariz and Sa'eed bin Al-Musayyab that: Abu Hurairah said: "I heard the Messenger of Allah (ﷺ) say: 'If you say to your companion: Listen attentively on a Friday when the Imam is delivering the khutbah, then you have engaged in idle talk.'"

Sunan an-Nasa'i (Book 14, Hadith 1413)

and

Abu Huraira reported Allah's Messenger (ﷺ) as saying:

If you (even) ask your companion to be quiet on Friday while the Imam is delivering the sermon, you have in fact talked irrelevance.

Sahih Muslim (Book 7, Hadith 15)

Even if it relates to a good deed or some Islamic inquiry:

‘Ata’ bin Yasar narrated from Ubayy bin Ka’b: “The Messenger of Allah (ﷺ) recited Tabarak [Al-Mulk (67)] one Friday, while he was standing and reminding us of the Days of Allah (i.e., preaching to us). Abu Darda’ or Abu Dharr raised an eyebrow at me and said: ‘When was this Surah revealed? For I have not heard it before now.’ He (Ubayy) gestured to him that he should remain silent. When they finished, he said: ‘I asked you when this Surah was revealed and you did not answer me.” Ubayy said: ‘You have gained nothing from your prayer today except the idle talk that you engaged in.’ He went to the Prophet (ﷺ) and told him about that, and what Ubayy had said to him. The Messenger of Allah (ﷺ) said: ‘Ubayy spoke the truth.’

Sunan Ibn Majah (Book 5, Hadith 1165)

According to the majority of the Ulema, the reason for this prohibition is that listening to the Friday prayer sermon is obligatory (wajib), as it takes the place of two of the rakahs of the noon prayer, so things offensive during the prayer are offensive while listening to the sermon.

Also please note that an exception is made from that in the case of speaking to the Imam, or the Imam speaking to the worshippers for some important reason.

Narrated Anas bin Malik:

In the lifetime of Allah's Messenger (ﷺ) (p.b.u.h) the people were afflicted with a (famine) year. While the Prophet was delivering the Khutba (sermon) on the pulpit on a Friday, a Bedouin stood up and said, "O Allah's Messenger (ﷺ)! The livestock are dying and the families (offspring) are hungry: please pray to Allah to bless us with rain." Allah's Messenger (ﷺ) raised both his hands towards the sky and at that time there was not a trace of cloud in they sky. Then the clouds started gathering like mountains. Before he got down from the pulpit I saw rainwater trickling down his beard. It rained that day, the next day, the third day, the fourth day and till the next Friday, when the same Bedouin or some other person stood up (during the Friday Khutba) and said, "O Allah's Messenger (ﷺ)! The houses have collapsed and the livestock are drowned. Please invoke Allah for us." So Allah's Messenger (ﷺ) raised both his hands and said, "O Allah! Around us and not on us." Whichever side the Prophet (ﷺ) directed his hand, the clouds dispersed from there till a hole (in the clouds) was formed over Medina. The valley of Qanat remained flowing (with water) for one month and none, came from outside who didn't talk about the abundant rain.

Sahih al-Bukhari (Book 15, Hadith 28)

Thus those who attend Friday prayers have to be silent and listen attentively to the Imam. It is not permissible to speak whilst the Imam is delivering the khutbah, except in cases of necessity such as saving a blind man from falling or if the khateeb makes a mistake in reciting a verse that alters the meaning, or if he omits a phrase from a verse or some other reasons in which the Imam may speak for a purpose include problems with the loudspeakers, in which the imam may speak to the engineer and ask him to see what is wrong.

Based on how you frame your question, I assume you didn't have the intention to make a mistake. In Islam all actions are based on your niyah. Inshallah, Allah will bless you with His Mercy.

But now that you know what is the etiquette, inshallah you will also be more attentive and careful I hope :)

Salaam!

References: https://islamqa.info/en/45651