Sunan Ibn Majah Book 7, Hadith 1704

حَدَّثَنَا عَلِيُّ بْنُ مُحَمَّدٍ، حَدَّثَنَا عَبْدُ اللَّهِ بْنُ نُمَيْرٍ، عَنْ عُبَيْدِ اللَّهِ، عَنْ نَافِعٍ، قَالَ سَأَلْتُ أُمَّ سَلَمَةَ عَنِ الرَّجُلِ، يُصْبِحُ، وَهُوَ جُنُبٌ، يُرِيدُ الصَّوْمَ؟ قَالَتْ: كَانَ رَسُولُ اللَّهِ ـ صلى الله عليه وسلم ـ يُصْبِحُ جُنُبًا مِنَ الْوِقَاعِ، لاَ مِنِ احْتِلاَمٍ، ثُمَّ يَغْتَسِلُ وَيُتِمُّ صَوْمَهُ ‏.‏

It was narrated that Nafi’ said:“I asked Umm Salamah about a man who gets up in the morning when he is in a state of sexual impurity and wants to fast. She said: “The Messenger of Allah (ﷺ) used to get up in the morning in a state of sexual impurity after having intercourse, not from a wet dream, then he would take a bath and complete his fast.’”