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]
Original Hadith
"«إذا قلتَ لصاحبك: أَنْصِتْ يوم الجمعة والإمام يَخْطُبُ، فقد لَغَوْتَ».
[صحيح.] - [متفق عليه."