Abu Bakr bin Abd al-Rahman says that Marwan sent him to Sayyidah Umm Salamah (may Allah be pleased with her) to ask her about a man who wakes up in the morning in a state of janabah: should he fast? She said that the Messenger of Allah (peace and blessings be upon him) would wake up in the morning in a state of janabah, and the janabah was from intercourse, not from a wet dream; then he (peace and blessings be upon him) would neither break his fast nor make it up.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 7993