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 Messenger of Allah (peace and blessings be upon him), "Can any one of us sleep in a state of janabah (major ritual impurity)?" The Prophet (peace and blessings be upon him) said: "When he intends to sleep, he should perform ablution."