Silsilat al-Ahadith al-Sahihah

The Messenger of Allah (peace and blessings be upon him) said: When the circumcised parts of (a man and a woman) meet, then ghusl (ritual bath) becomes obligatory. With these words, this hadith is narrated from Lady Aisha, Abdullah bin Amr bin Al-As, and Abu Hurairah (may Allah be pleased with them) and others.