The Book of Menstruation (Kitab Al-Haid)

Muslim :: Book 3 : Hadith 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.

Source materials are from the University of Southern California MSA site
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