Sahih Muslim Book 003, Hadith Number 0682.
Chapter : Abrogation of (the command that) bath is obligatory(only) because of seminal emission and instead contact of the circumcised parts makes bath obligatory.
Abu Huraira reported: The Apostle of Allah (may peace be upon him) said: When a man has sexual intercourse, bathing becomes obligatory (both for the male and the female). In the Hadith of Matar the words are: Even if there is no orgasm. Zuhair has narrated it with a minor alteration of words.