Sunan an-Nasa'i 191
سنن النسائي#191SahihIt was narrated from Abu Hurairah that the Messenger of Allah (ﷺ) said:"When (a man) sits between the four parts of his wife's body and exerts himself, then Ghusl becomes obligatory
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Abu GhuddahSahih
Al-AlbaniSahih
Zubair Ali ZaiSahih - Agreed Upon
In-book reference: 1:192