Musnad Ahmad 1166:2

'Abd al-Razzaq and Ibn Bakr narrated to us, they said: Ibn Jurayj narrated to us, he said: 'Ata' informed me, from Umm Hani' bint Abi Talib, she said: "I entered upon the Prophet, peace and blessings of Allah be upon him, on the day of the Conquest while he was in a tent of his. I found that he had bathed with water that was in a platter; I could see the trace of dough in it. And I found him praying the Duha (forenoon) prayer." I said: "Do you think this report of Umm Hani' is established?" He said: "Yes." Ibn Bakr said: "The Duha."