(13) باب صِحَّةِ صَوْمِ مَنْ طَلَعَ عَلَيْهِ الْفَجْرُ وَهُوَ جُنُبٌ
Abu Bakr b. 'Abd al-Rahman b. al-Harith b. Hisham reported on the authority of 'A'isha and Umm Salama, the wives of the Messenger of Allah (ﷺ):
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.
Reference: Sahih Muslim 1109 d
In-book reference: Book 13, Hadith 98
USC-MSA web (English) reference(deprecated numbering scheme): Book 6, Hadith 2454