Ibn Hibban

Ubaidullah bin Abdullah bin Harith narrates from his father: I investigated this matter and was very eager to find someone who could inform me about it—whether the Prophet (peace be upon him) performed the Duha prayer. I found only Lady Umm Hani (may Allah be pleased with her), who informed me about this: She told me that on the day of the conquest of Makkah, after the day had advanced, the Prophet (peace be upon him) arrived. By his order, a cloth was hung for his privacy, and he performed ghusl (ritual bath). Then he stood up and performed eight rak‘ahs. I cannot determine whether his standing, his bowing, or his prostration was longer; all of these were nearly equal in length. Lady Umm Hani (may Allah be pleased with her) states: I never saw him perform voluntary prayers at that time, either before or after this occasion.