Abu Bakr bin Abdur Rahman narrates that I and my father were with the governor of Madinah, Marwan bin Hakam, when mention was made regarding Abu Hurairah (may Allah be pleased with him) that he says: "Whoever wakes up in a state of major ritual impurity (janabah) should break his fast that day." Marwan said: O Abdur Rahman! I adjure you to go to the Mothers of the Believers, Lady Aisha and Lady Umm Salamah (may Allah be pleased with them both), and definitely ask them about this. Abu Bakr says: Abdur Rahman went and I also went with him until we came to Lady Aisha (may Allah be pleased with her). Abdur Rahman greeted her and said: O Mother of the Believers! We were with Marwan when it was mentioned before us that Abu Hurairah (may Allah be pleased with him) said: "Whoever wakes up in a state of major ritual impurity (janabah) will break his fast that day." Lady Aisha (may Allah be pleased with her) said: "O Abdur Rahman! The matter is not as Abu Hurairah (may Allah be pleased with him) has said. Will you turn away from the practice of the Messenger of Allah (peace and blessings be upon him)?" Abdur Rahman said: By Allah! Certainly not, O Aisha (may Allah be pleased with her)! So Lady Aisha (may Allah be pleased with her) said: "I bear witness upon the Messenger of Allah (peace and blessings be upon him) that he would wake up in a state of major ritual impurity (janabah) due to intercourse, not due to a wet dream, and then he would fast that day." Abu Bakr says: Then we left and came to Lady Umm Salamah (may Allah be pleased with her). We asked her about this as well, and she said the same as Lady Aisha (may Allah be pleased with her) had said. Abu Bakr says: We left until we came to Marwan. Abdur Rahman told him what both of them (the pure wives of the Prophet, peace and blessings be upon him) had said. So Marwan said: O Abu Muhammad! I adjure you to definitely mount the riding animal standing at the door and go to Abu Hurairah (may Allah be pleased with him) and inform him about this. Abu Bakr says: Abdur Rahman mounted, and I also mounted with him, until we came to Abu Hurairah (may Allah be pleased with him). Abdur Rahman conversed with him for a while (about other matters), then mentioned this incident to him. So Abu Hurairah (may Allah be pleased with him) said: "I have no knowledge of this; someone who informed me told me so."
Hadith Referenceمسند الإمام الشافعي / كتاب الصيام / 649
Hadith Takhrijاخرجه البخاري، الصوم، باب الصائم، يصبح جنبا (1925) ، (1926) ، ومسلم، الصيام، باب صحة صوم من طلع عليه الفجر وهو جنب (1109)۔