when anyone sits between the four parts of a woman and the parts (of the male and female) which are circumscised join together, then bath becomes obligatory. (Using translation from Abū Dāʾūd 216)
"إِذا قَعَد بين شُعَبها الأرْبَع وألزَق الخِتانَ بالخِتْانِ فقد وَجَبَ الغُسْلُ" .