Ibn Abbas (may Allah be pleased with them both) said: I spent the night at the house of my maternal aunt Maymunah (may Allah be pleased with her), and the Prophet (peace and blessings be upon him) was with her that night. He (peace and blessings be upon him) performed ablution, then stood up to pray, and I stood on his left; he took hold of me and placed me on his right. He (peace and blessings be upon him) prayed thirteen rak'ahs that night, then slept until he breathed audibly, and whenever he (peace and blessings be upon him) slept he would breathe audibly. Then the mu'adhdhin came, and he (peace and blessings be upon him) went out and prayed, but he did not perform ablution.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 13385