Sahih Muslim
The Book of Menstruation (Kitab Al-Haid)
Book Number: 003 / Hadith Number: 602
Ibn Umar reported: Umar b. al-Khattab said to the Messenger of Allah (may peace be upon him), that he became Junbi during the night. The Messenger of Allah (may peace be upon him) said to him: Perform ablution, wash your sexual organ and then go to sleep.