Musnad Ahmad 1153:569

Abu al-Yaman narrated to us, he said: Shu'ayb informed us, from al-Zuhri, he said: 'Urwah ibn al-Zubayr narrated to me, that 'Aishah, the wife of the Prophet, may Allah bless him and grant him peace, said: The Prophet, may Allah bless him and grant him peace, entered upon me while a woman from the Jews was with me, and she was saying to me: "Do you realize that you will be tested in the graves?" The Prophet, may Allah bless him and grant him peace, was alarmed and said: "It is only the Jews who are tested." 'Aishah said: We remained for some nights, then the Prophet, may Allah bless him and grant him peace, said: "Do you realize that it has been revealed to me that you will be tested in the graves?" 'Aishah said: So I heard the Messenger of Allah, may Allah bless him and grant him peace, after that, seeking refuge from the punishment of the grave.