Musannaf Ibn Abi Shayba 3:1798

4175. Ibn ‘Ulayyah narrated to us, from ‘Abd al-‘Aziz ibn Suhayb, from Anas, who said: The prayer was called, and the Messenger of Allah (may Allah bless him and grant him peace) was in private conversation with a man in the corner of the mosque. He did not stand for the prayer until the people had fallen asleep.