The Messenger of Allah (ﷺ) at times got up in the morning in a state of junub on account of having a sexual intercourse (with his wives during night) but not due to sexual dreams in the month of Ramadan, and would observe fast.
Sahih Muslim Book 13, Hadith 98
← Previous Hadith Abu Bakr reported that Marwan sent him to Umm Salama to ask whether a person should observe fast who is in a state of junub and the dawn breaks upon him, whereupon she said that the Messenger of Allah (ﷺ) (was at times) junbi on account of intercourse and not due to sexual dream, and the dawn broke upon him, but he neither broke the fast nor recompensed.

Sahih Muslim Book 13, Hadith 97 Next Hadith → Messenger of Allah, (the time) of prayer overtakes me as I am in a state of junub; should I observe fast (in this state)? Upon this the Messenger of Allah (ﷺ) said: (At times the time) of prayer overtakes me while I am in a state of junub, and I observe fast (in that very state), whereupon he said: Messenger of Allah, you are not like us Allah has pardoned all your sins, the previous ones and the later ones. Upon this he (the Holy Prophet) said: By Allah, I hope I am the most God-fearirg of you, and possess the best knowledge among you of those (things) against which I should guard.

Sahih Muslim Book 13, Hadith 99