From Sahih Muslim (Hadith 2594):
Sulaiman b. Yasar reported that he asked Umm Salama whether a person (who gets up) in the morning in a state of junub should observe fast. She said:The Messenger of Allah (ﷺ) (at times) got up in the morning in a state of junub, not because of sexual dreams (but on account of intercourse at night), and then observed fast
Reference: Muslim 2594