(8) باب الغسل وحكم الجنب
Narrated Abu Huraira (rad):
Allah's Messenger (ﷺ) said that, "If one of you sits between her legs (of a woman) and penetrates her, Ghusl (bath) is obligatory." [Agreed upon].
Reference: Bulugh al-Maram 110
In-book reference: Book 1, Hadith 130
English translation: Book 1, Hadith 116