Musnad Ahmad 32:374

Muhammad ibn Ja‘far narrated to us, Shu‘bah narrated to us, from ‘Abd al-‘Aziz, from Anas, who said: "The prayer was called, and a man was speaking privately with the Messenger of Allah, may Allah bless him and grant him peace. He continued to speak privately with him until his companions fell asleep, then he stood and prayed."