Sahih Muslim Book 3, Hadith Number 623.

Chapter : Bathing after sexual intercourse or seminal emission.

‘Aisha reported: When the Messenger of Allah (may peace be upon him) took a bath because of sexual intercourse, he called for a vessel and took a handful of water from it and first (washed) the right side of his head, then left, and then took a handful (of water) and poured it on his head.