It is narrated from Sayyidah Umm Salamah (may Allah be pleased with her); she said that the Messenger of Allah (peace and blessings be upon him) would reach the morning in a state of major ritual impurity (janabah) from being with his wives, not from a wet dream, and then remain fasting.
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 19900