It was narrated that 'Aishah the wife of the Prophet said:
"When the two circumcised parts meet, then bath is obligatory. The Messenger of Allah and I did that, and we bathed." (RU)
English reference (RU): Vol. 1, Book 1, Hadith 608 (RU)
Arabic reference (RU): Book 1, Hadith 651 (RU)