Musnad Ahmad 1153:2087

Uthman ibn Umar narrated to us, he said: Yunus informed us, from al-Zuhri, from Urwah, from Aisha, that the Messenger of Allah (peace and blessings of Allah be upon him) entered upon her while a Jewish woman was with her, and she was saying: "Do you realize that you will be tested in the graves?" The Messenger of Allah (peace and blessings of Allah be upon him) was alarmed and said: "It is only the Jews who are tested." Aisha said: We remained for some nights, then the Messenger of Allah (peace and blessings of Allah be upon him) said: "Do you realize that it has been revealed to me that you will be tested in the graves?" Aisha said: I heard the Messenger of Allah (peace and blessings of Allah be upon him) afterwards seeking refuge from the punishment of the grave. *** Uthman ibn Umar narrated to us, he said: Yunus informed us, from al-Zuhri, from Urwah, from Aisha, that she said: "The Messenger of Allah (peace and blessings of Allah be upon him) used to pray eleven rak'ahs at night, and that was his prayer. He would prostrate in the prostration of that for the duration of what one of you would take to recite fifty verses before he would raise his head. And he would pray two rak'ahs before the dawn, then he would lie down on his right side until the caller to prayer came to him."