It is narrated from Sayyiduna Abdullah bin 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): "Can one of us sleep while in a state of janabah?" He (peace and blessings be upon him) said: "Yes, let him perform ablution, then sleep, until he performs the ritual bath whenever he wishes." When Abdullah bin Umar (may Allah be pleased with them both) intended to sleep while in a state of janabah, he would pour water over his hands, then wash his private part with his left hand, then wash the hand with which he had washed his private part, then rinse his mouth, sniff water into his nose, splash water into his eyes, wash his face and his hands up to and including the elbows, and wipe his head, then sleep. And if he intended to eat something while in a state of janabah, he would do the same.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 972