عن أبي هُريرة رضي الله عنه مرفوعًا: «إذا قلتَ لصاحبك: أَنْصِتْ يوم الجمعة والإمام يَخْطُبُ، فقد لَغَوْتَ».
[صحيح] - [متفق عليه]
Abu Hurayrah (may Allah be pleased with him) reported that the Prophet (may Allah's peace and blessings be upon him) said: "If you said to your companion: 'Be quiet and listen' on Friday while the Imām is delivering the sermon, then you would be guilty of idle talk."
Sahih/Authentic. - [Al-Bukhari and Muslim]
From the greatest rites of Friday is the two sermons, and one of its purposes is to advise and direct the people. One of the obligatory manners the listener has to observe is to listen attentively to the orator in order to contemplate the admonition. That is why the Prophet (may Allah's peace and blessings be upon him) warned against speaking, even with a few words, such as forbidding one's companion from speaking by merely saying: "Be quiet and listen." Whoever speaks while the Imām is delivering the sermon is guilty of idle talk, and is thus deprived of the virtue of attending the Friday prayer, because he has done something that distracts him as well as others from listening to the sermon.