The Messenger of Allah ﷺ said, "When the two circumcised parts meet and the head of the penis disappears, the ritual bath becomes obligatory."
حدثنا أبو بكر بن أبي شيبة حدثنا أبو معاوية عن حجاج
قال رسول الله ﷺ إذا التقى الختانان وتوارت الحشفة فقد وجب الغسل
[Its chain is daif] Busiri said, this chain is daif due to the weakness of Hajjaj, who is Ibn Artah, and his tadlis, as he narrated it using "an" (indicating a possible break in the chain). The hadith has weak corroborating narrations, but the previous hadith (608) makes it unnecessary.