Sahih Muslim 707
صحيح مسلم#707SahihAbu Sa'id al-Khudri reported:The Messenger of Allah (ﷺ) said: When anyone amongst you has sexual intercourse with his wife and then he intends to repeat it, he should perform ablution. In the hadith transmitted by Abu Bakr. (the words are):" Between the two (acts) there should be an ablution," or he (the narrator) said:" Then he intended that it should be repeated
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih Muslim is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 3:29