The Prophet ﷺ said, "When a man sits between her four limbs and exerts himself upon her, the bath becomes obligatory."
عن النبي ﷺ أنه قال: إذا جلس بين شعبها الأربع، ثم جهدها فقد وجب الغسل.
Bukhari narrated it in the chapter on ghusl (291) and Muslim in the chapter on menstruation (348), both from the hadith of Hisham Dastawai, from Qatada, from Hasan, from Abu Rafi, from Abu Hurairah. Muslim added, through the route of Matar, from Hasan, "even if no emission occurs."As for his saying, "the two circumcised parts," this dual form refers to the circumcised part of the man and the circumcised part of the woman. The circumcision of the woman is the cutting of a small piece of skin at the top of her private part, resembling a rooster's comb, with a thin layer of skin separating it from the place of entry of the male organ.