Chapter: Greeting (prayers upon entering the masjid) while the Imam is preaching
Jabir reported that Sulaik Ghatafani came on Friday (for prayer) while the Messenger of Allah ( صلی اللہ علیہ وسلم ) was sitting on the pulpit. Sulaik also sat down before observing prayer. The Apostle of Allah ( صلی اللہ علیہ وسلم ) said: Have you observed two rak'ahs? He said: No. He (the Holy Prophet) said: Stand and observe them
Authentic