It was the practice of the Prophet (peace and blessings be upon him):
"When the two circumcised parts met, he (peace and blessings be upon him) would perform the ritual bath (ghusl)."
Hadith Referenceصحیح الجامع الصغیر / حرف الكاف / 4684
Hadith Gradingالألبانی:صحيح
Hadith Takhrij[الطحاوي] عن عائشة. الصحيحة ٢٠٦٣: حم.