It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that Umar bin al-Khattab (may Allah be pleased with him) mentioned to the Messenger of Allah (peace and blessings be upon him): If I become junub (in a state of major impurity) at night, (what should I do)? The Messenger of Allah (peace and blessings be upon him) said: "Perform ablution, wash your private part, and then sleep."
(b) It is narrated from Abdullah bin Dinar that he (peace and blessings be upon him) said: "Wash your dhakar (private part) and perform ablution."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 964