Abu Hurairah said: "I heard the Messenger of Allah ﷺ say: 'If you say to your companion: Listen attentively on a Friday when the Imam is delivering the khutbah, then you have engaged in idle talk.'" (Using translation from Nasāʾī 1402)
سَمِعْتُ رَسُولَ اللهِ ﷺ يَقُولُ «إِذَا قُلْتَ لِصَاحِبِكَ يَوْمَ الْجُمُعَةِ وَالْإِمَامُ يَخْطُبُ أَنْصِتْ فَقَدْ لَغَوْتَ»