Musnad Ahmad 1156:189

'Affan narrated to us, Hammam narrated to us, from Qatadah, that Abu 'Iyad narrated that Marwan sent [a messenger] to Umm Salamah, the wife of the Prophet (peace and blessings of Allah be upon him), and he sent her freedman to her. She said: "The Messenger of Allah (peace and blessings of Allah be upon him) would wake up in a state of major ritual impurity (junub), then he would fast and not break his fast." He said: So he returned to him and informed him. Then he sent to 'Aishah, and he sent her freedman or her servant, Dhakwan, to her. She said: "The Messenger 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, then he would fast and not break his fast." He said to him: "Go to Abu Hurairah and inform him." So he went to Abu Hurairah and informed him of [what] Umm Salamah and 'Aishah [said]. He said: "They are more knowledgeable."