Musnad Abu Ya'la al-Mawsili 117:35

Ibrahim ibn al-Hajjaj narrated to us, Hammad narrated to us, from Thabit, from Anas, who said: The night prayer (Isha) was called, and a man said: "O Messenger of Allah, I have a need." So he stood with him, speaking privately to him, until the people—or some of the people—became drowsy. Then he stood and prayed, and he did not mention ablution.