Musnad Ahmad 1803

Abu Bakr bin ‘AbdurRahman bin al-Harith bin Hisham said: "A"ishah and Umm Salamah, the wives of the Prophet (ﷺ) , said: The Messenger of Allah (ﷺ) would wake up junub from intimacy with his wife, and he would do ghusl before praying Fajr, then he would fast that day. He (the narrator) said: I mentioned that to Abu Hurairah and he said: I do not know; al-Fadl bin "Abbas (رضي الله عنه) told me this.