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
وَحَدَّثَنَا عَبْدُ الْوَارِثِ بْنُ عَبْدِ الصَّمَدِ، حَدَّثَنِي أَبِي، عَنْ جَدِّي، عَنِ الْحُسَيْنِ، قَالَ يَحْيَى وَأَخْبَرَنِي أَبُو سَلَمَةَ، أَنَّ عُرْوَةَ بْنَ الزُّبَيْرِ، أَخْبَرَهُ أَنَّ أَبَا أَيُّوبَ أَخْبَرَهُ أَنَّهُ، سَمِعَ ذَلِكَ، مِنْ رَسُولِ اللَّهِ صلى الله عليه وسلم .
Abu Ayyub reported that he had heard like this from the Messenger of Allah (ﷺ).
Reference : Sahih Muslim 347bIn-book reference : Book 3, Hadith 104USC-MSA web (English) reference : Book 3, Hadith 681