Musnad Ahmad 1153:1793

Isma'il narrated to us, he said: Ayyub informed us, from 'Ikrimah ibn Khalid, from Abu Bakr ibn 'Abd al-Rahman ibn al-Harith, who said: I am the most knowledgeable of people regarding this hadith. He said: It reached Marwan that Abu Hurairah was narrating from the Messenger of Allah (peace and blessings of Allah be upon him): "Whoever is overtaken by the morning while he is in a state of major ritual impurity (junub), then he should not fast on that day." So he sent to 'A'ishah to ask her about that. He (Abu Bakr) went with him and asked her. She said: "The Messenger of Allah (peace and blessings of Allah be upon him) used to wake up in the morning in a state of major ritual impurity, without having had a wet dream, and then he would fast." He returned to Marwan and told him. He (Marwan) said: "Go to Abu Hurairah and tell him." He said: "He is my neighbor, and I dislike confronting him with what he dislikes." He said: "I command you to go to him." He said: So he met him and said: "O Abu Hurairah, by Allah, I was reluctant to confront you with what you dislike, but the Amir commanded me." He said: So he told him. He (Abu Hurairah) said: "Al-Fadl narrated it to me."