Musnad Abu Ya'la al-Mawsili 150:358

Hadaba narrated to us, Mubarak bin Fudala narrated to us, al-Hasan narrated to us, from Sa’d bin Hisham bin ‘Amir, who said: I was a man who followed the authorities, so my father took me and imprisoned me. Mubarak said: And I do not know him except that he said: And he shackled me. He said to me: By Allah, you shall not go out until you have memorized the Book of Allah. So I memorized the Book of Allah, and Allah benefited me through it, and the world departed from me, and I began to dislike marrying and doing [worldly things]. So I entered upon ‘Aisha and said: Sa’d bin Hisham bin ‘Amir. She said: May Allah have mercy on ‘Amir; he was struck on the day of Uhud as a martyr. He said: I said: O Mother of the Believers, I wish to remain celibate, so I came to ask you about that. She said: O Hisham, do not remain celibate, for Allah said: "There has certainly been for you in the Messenger of Allah an excellent pattern," and the Messenger of Allah (peace and blessings of Allah be upon him) married and had children. He said: I said: O Mother of the Believers, tell me about the character of the Messenger of Allah (peace and blessings of Allah be upon him). She said: O my son, do you not read the Qur’an? Allah said: "And indeed, you are of a great moral character." The character of Muhammad is the Qur’an. He said: I said: O Mother of the Believers, tell me about the prayer of the Messenger of Allah (peace and blessings of Allah be upon him). She said: O my son, and who can endure the prayer of the Messenger of Allah? The Messenger of Allah (peace and blessings of Allah be upon him) used to, when he prayed, pray two rak’ahs, then sleep for a while, then stand and pray two rak’ahs, and two, and two, and two, and two, and one—or she said: He would pray two, and two, and two, and two, and one—a prayer after the ‘Isha [prayer] of nine rak’ahs and eleven [rak’ahs]. When the Messenger of Allah (peace and blessings of Allah be upon him) grew old and his flesh increased, he prayed two rak’ahs, and two, and one, and he prayed two rak’ahs while he was sitting.