(36) باب الإِنْصَاتِ يَوْمَ الْجُمُعَةِ وَالإِمَامُ يَخْطُبُ
Narrated Abu Huraira:
Allah's Messenger (ﷺ) (p.b.u.h) said, "When the Imam is delivering the Khutba, and you ask your companion to keep quiet and listen, then no doubt you have done an evil act."
Reference: Sahih al-Bukhari 934
In-book reference: Book 11, Hadith 58
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 2, Book 13, Hadith 56