Musnad Ahmad 32:1888

'Affan narrated to us, Hammad ibn Salamah narrated to us, he said: Thabit informed us, from Anas, who said: "The prayer for the final Isha was established one night, and a man said: 'O Messenger of Allah, I have a need.' So he stood whispering to him until the people, or some of the people, became drowsy. Then he prayed and did not mention ablution."