وَقَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ : " إِذَا قُلْتَ لِلنَّاسِ : أَنْصِتُوا ، وَهُمْ يَتَكَلَّمُونَ ، فَقَدْ أَلْغَيْتَ عَلَى نَفْسِكَ " .
And the Noble Prophet (peace and blessings be upon him) said: When the Imam is delivering the Friday sermon and you say to your companion, "Be quiet," then you have engaged in idle talk.