The Book of Menstruation
3/21. Chapter:
At the beginning of Islam, intercourse did not necessitate ghusl unless semen was emitted, then that was abrogated and ghusl becomes obligatory for intercourse
Sahih Muslim
حَدَّثَنَا أَبُو الرَّبِيعِ الزَّهْرَانِيُّ، حَدَّثَنَا حَمَّادٌ، حَدَّثَنَا هِشَامُ بْنُ عُرْوَةَ، ح وَحَدَّثَنَا أَبُو كُرَيْبٍ، مُحَمَّدُ بْنُ الْعَلاَءِ - وَاللَّفْظُ لَهُ - حَدَّثَنَا أَبُو مُعَاوِيَةَ، حَدَّثَنَا هِشَامٌ، عَنْ أَبِيهِ، عَنْ أَبِي أَيُّوبَ، عَنْ أُبَىِّ بْنِ كَعْبٍ، قَالَ سَأَلْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم عَنِ الرَّجُلِ يُصِيبُ مِنَ الْمَرْأَةِ ثُمَّ يُكْسِلُ فَقَالَ " يَغْسِلُ مَا أَصَابَهُ مِنَ الْمَرْأَةِ ثُمَّ يَتَوَضَّأُ وَيُصَلِّي " .
Ubayy Ibn Ka'b reported: I arked the Messenger of Allah (ﷺ) about a man who has sexual intercourse with his wife, but leaves her before orgasm. Upon this he (the Holy Prophet) said: He should wash the secretion of his wife, and then perform ablution and ofier prayer.
Reference : Sahih Muslim 346aIn-book reference : Book 3, Hadith 101USC-MSA web (English) reference : Book 3, Hadith 677