It is narrated from Sayyidah Umm Salamah (may Allah be pleased with her) that the Prophet (peace and blessings be upon him) would wake in the morning in a state of major ritual impurity (janabah), then perform the ritual bath (ghusl) and fast.
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 19973