Musnad Ahmad 1153:2064

Rawh narrated to us, Sa’id narrated to us, from Qatadah, from ‘Abd Rabbih, from Abu ‘Iyad, from ‘Abd al-Rahman ibn al-Harith ibn Hisham, that Marwan ibn al-Hakam sent him to Umm Salamah and ‘Aishah. He said: So I came to the servant of Umm Salamah, Nafi’, and I sent him to her. He returned to me and informed me that Umm Salamah said: "The Messenger of Allah, peace and blessings of Allah be upon him, would wake up in a state of janabah (major ritual impurity) without having had a wet dream, then he would wake up fasting." He said: Then he met the servant of ‘Aishah, Dhakwan Abu ‘Amr, and sent him to her. He asked her about that, and she informed him: "That the Prophet of Allah, peace and blessings of Allah be upon him, would wake up in a state of janabah without having had a wet dream, then he would wake up fasting."