Sahih Bukhari
Military Expeditions led by the Prophet (pbuh) (Al-Maghaazi)
Volume: 005 / Book Number: 059 / Hadith Number: 587
Narrated Ibn Laila:
None informed us that he saw the Prophet offering the Duha (i.e. forenoon) prayer, except Um Ham who mentioned that the Prophet took a bath in her house on the day of the Conquest (of Mecca) and then offered an eight Rakat prayer. She added, "I never saw the Prophet offering a lighter prayer than that prayer, but he was performing perfect bowing and prostrations."