(a) Layth bin Sa'd narrated it in the same way.
(b) It is narrated from Sayyidah Aishah (may Allah be pleased with her) that when the Messenger of Allah (peace and blessings be upon him) intended to sleep while in a state of janabah, he would wash his private part and perform an ablution like the ablution for prayer, then sleep.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 967