It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that Sayyiduna Umar (may Allah be pleased with him) asked the Prophet (peace and blessings be upon him) that I become junub (in a state of major ritual impurity) at night. The Prophet (peace and blessings be upon him) instructed him to wash his private parts and perform ablution.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 5190