Musnad Ahmad 25:1316

Bahz narrated to us, Shu'bah narrated to us, Al-Hakam narrated to me, he said: I heard Sa'id ibn Jubayr narrating from Ibn Abbas, he said: I spent the night in the house of my maternal aunt Maymunah. The Messenger of Allah (peace and blessings of Allah be upon him) prayed the Isha prayer, then he came and prayed four [rak'ahs]. Then he said: "Has the little boy—or the boy—fallen asleep?"—Shu'bah said: Or something similar to this—he said: Then he slept. He said: Then he stood up and performed ablution. He said: I do not remember his ablution. He said: Then he stood up and prayed, so I stood to his left. He said: So he placed me to his right, then he prayed five rak'ahs. He said: Then he prayed two rak'ahs. He said: Then he slept until I heard his snoring—or his breathing—then he prayed two rak'ahs, then he went out for the prayer.