Musnad Ahmad 1156:190

Muhammad ibn Ja‘far 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: I met her servant, Nafi‘, so I sent him to her, and he asked her. He said: He returned to me and informed me that she said: "The Prophet of Allah, peace and blessings of Allah be upon him, would wake up in a state of major ritual impurity (junub) from intercourse, not from a wet dream, and then he would wake up fasting." He said: So I came to Marwan and informed him. He said: "I adjure you to go to Abu Hurayrah and inform him of it." So I went to him and informed him, and he said: "They are more knowledgeable."