The Book of Menstruation (Kitab Al-Haid)
Muslim :: Book 3 : Hadith 677
Ubayy Ibn Ka'b reported: I arked the Messenger of Allah (may peace be upon him) about a man who has sexual intercourse with his wife, but leaves her before orgasm. Upon this he (the Holy Prophet) said: He should wash the secretion of his wife, and then perform ablution and ofier prayer.