The Messenger of Allah ﷺ would wake up in the morning in a state of major ritual impurity, then bathe and fast that day.
حدثنا حماد حدثنا أفلح عن القاسم
كان رسول الله ﷺ يصبح وهو جنب فيغتسل ويصوم يومه
Its isnad is sahih, mentioned previously at 25377.