Jarir bin Abdullah (radi Allahu anhu) reported, “The Messenger of Allah (sal Allahu alaihi wa sallam) asked me on the occasion of the Farewell Pilgrimage to tell the people to keep silent, then He (sal Allahu alaihi wa sallam) said, ‘Do not revert to disbelief after me, chopping the heads of one another.’”
[Sahih Al-Bukhari and Muslim]
We benefit from this Hadith that silence is a prerequisite of listening to a sermon, and a Khatib (the one who is delivering a sermon) is allowed to ask his audience to observe silence so the audience will be able to listen to the sermon attentively.
So whenever we are listening to a sermon and Allah’s words are being recited and the Prophet’s (sal Allahu alaihi wa sallam) ahadith are being mentioned we should be silent and receptive so as to benefit from what we are hearing.
And Allah knows best!