When the two circumcised parts meet, the bath becomes obligatory. I did this with the Messenger of Allah ﷺ, and we both performed the bath.
حدثنا علي بن محمد الطنافسي وعبد الرحمن بن إبراهيم الدمشقي قالا حدثنا الوليد بن مسلم حدثنا الأوزاعي أنبأنا عبد الرحمن بن القاسم أخبرنا القاسم بن محمد
إذا التقى الختانان فقد وجب الغسل فعلته أنا ورسول الله ﷺ فاغتسلنا
[Its isnad is sahih] Tirmidhi recorded it, in the Book of Purification, chapter on what has been said regarding "when the two circumcised parts meet, ghusl becomes obligatory," hadith no. 108, and he said, hasan sahih. Ibn Hibban and Ibn Qattan also graded it sahih.