Abu Bakr bin Abd al-Rahman relates that Marwan bin al-Hakam sent him to Sayyidah Umm Salamah (may Allah be pleased with her) to ask her: If a man reaches the morning in a state of major impurity (janabah), should he fast? She said: the Messenger of Allah (peace and blessings be upon him) would reach the morning in a state of janabah from intercourse, not from a wet dream, and he would neither break his fast nor make it up.
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 20273