“If you say to your companions: ‘Be quiet’ on a Friday while the Imam is delivering the sermon, you have engaged in Laghw (idle talk or behaviour).” (Using translation from Ibn Mājah 1110)
أَنَّ النَّبِيَّ ﷺ قَالَ إِذَا قُلْتَ لِصَاحِبِكَ وَالْإِمَامُ يَخْطُبُ أَنْصِتْ فَقَدْ لَغَوْتَ