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]

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