Sunan Ibn Majah Book 1, Hadith 207
The Prophet performed ablution using (the water in) a vessel made of brass.
She had a tub of brass. She said: "I used to comb the hair of the Messenger of Allah in it."
"The Messenger of Allah would fall asleep until he was breathing deeply, then he would get up and offer the prayer, and he did not perform ablution." (Hasan) Tanafisi said: "Waki` said: 'She meant while he was prostrating (he would sleep).'"