Is it permissible for the imam to deliver a lesson or sermon immediately after the prayer while some people are still praying?

The questioner: In the sense of: Is it permissible for the imam to narrate a hadith to the worshippers after the prayer?

The Shaykh: You, Abu 'Adnan, is this your question?

The questioner: This is my question.

The Shaykh: The answer is: If the imam or anyone else wants to deliver a lesson, sermon, or advice, he must either wait until the worshippers have finished their prayers—meaning the voluntary prayer after the obligatory one—or announce to them that he intends to deliver a sermon, a word, or advice. This is so that, first, they may pay attention to it, and second, so that he does not disturb them in their prayers. This disturbance is not permissible. If the teacher, whether he is the imam or not, imposes his lesson, lecture, or advice on the worshippers before they have finished their prayers, he is encroaching upon them. The Messenger of Allah (peace be upon him) used to say: . Therefore, starting the lesson before the worshippers have finished their prayers disturbs them and consequently harms them, so it is not permissible. Thus, as I said, he must either wait until they are finished or ask for their permission, so that he does not fall into the forbidden disturbance mentioned in the authentic hadith.

The questioner: My brother Abu 'Abd al-Rahman...

The Shaykh : Yes?

The questioner: I would like to clarify a point regarding the matter... The imam, Abu Muhammad, has made it a common practice for the worshippers that after the obligatory 'Isha' prayer, everyone sits... daily, not for the first time. After every 'Isha' prayer, he sits and mentions one of the hadiths or one of the topics, and the worshippers sit until he finishes, then they pray the voluntary prayer. Except for the person who is in a hurry to pray the voluntary prayer... this is what... in the mosque, I mean.

The Shaykh: Yes, I say: Reality bears witness that if the imam starts his lecture as soon as he finishes his prayer, it is certainly disturbing to some of the worshippers. The mildest scenario we need to imagine is the one who joined the prayer late, missing one or two rak'ahs depending on whether the prayer is two, three, or four rak'ahs. This latecomer must, unlike the one we mentioned earlier who delays the voluntary prayer to finish part of the sermon, complete his prayer. As he (peace and blessings be upon him) said: . So if this latecomer wants to perform this rak'ah or more, and the imam stands up to preach and teach, it is certain that he will fall into the prohibition I quoted earlier from the Messenger of Allah (peace and blessings be upon him): .
If we assume a mosque or a prayer where there are absolutely no latecomers—and I think this is very rare, especially in the present time, due to people's lack of eagerness to catch the prayer at its beginning—then if we imagine this scenario, the detail I mentioned earlier applies: either the imam waits until they pray the voluntary prayer, if there is a voluntary prayer after the obligatory one, like the Fajr prayer for example, or there is nothing, or he asks for their permission. One of these two things is necessary. It is not permissible for the imam to impose his opinion on the worshippers, as some preachers do on Friday, for example, by lengthening the sermon and lengthening it, and reversing the prayer by shortening it excessively. This is contrary to the Sunnah which the Messenger of Allah (peace and blessings be upon him) explicitly stated when he said: . If you talk to preachers like these, they say: "My brother, we need to teach the people, and the people do not have the energy to attend gatherings of knowledge," and so on. This does not justify the imam in contradicting the Sunnah. He can, for example, deliver the sermon within the limits of the Sunnah as we mentioned; that is, to shorten it. Then, if it occurs to him during the sermon that a certain issue needs explanation, elaboration, and clarification, he tells them that this will be after the prayer. But to confine them—some of whom may be sick, or may have, for example, urinary incontinence or something similar—by confining them for half an hour in the sermon because he has decided in his mind to impose his teaching on the people against their will, no, this is not permissible. Therefore, I say: any imam, preacher, teacher, or instructor who wants to deliver a word after the end of the prayer must observe this point: he must not disturb the attendees, whether they are latecomers as we mentioned, which is necessary, or they are not latecomers but are engaged in dhikr.
You know, if Allah wills, that there are ten takbirs after the obligatory Maghrib and Fajr prayers. If the imam finishes his prayer and stands up to deliver a sermon or lesson, the one who wants to perform the ten takbirs will be disturbed. Especially since the hadith states that the one who wants to perform the ten takbirs should do so before changing his sitting position, and before talking to the person next to him, and so on. All these matters require this imam or this preacher to take them into proper consideration, otherwise he will have done wrong. He wants to teach the people, he wants to preach to them, and yet he falls into the opposite of what he teaches.
This is the summary of the answer to that question.

The questioner: So, Shaykh, the encroachment is not only on the latecomers or on the obligatory prayer followed by a voluntary prayer, but the encroachment is also on the dhikr after the prayer.

The Shaykh: Yes, that is so.