Abu Dawood: Hadith 1357

I spent a night with my maternal aunt Maimunah. The Messenger of Allah (ﷺ) came after the evening has come. He asked: Did the boy pray ? She said: Yes. Then he lay down till a part of night had passed as much as Allah willed; he got up, performed ablution and prayed seven or five rak'ahs, observing witr with them. He uttered the salutation only in the last of them.