Sahih Bukhari Volume 2, Book 20, Hadith Number 207.

Narated By Ibn Abu Laila : Only Um Hani told us that she had seen the Prophet (p.b.u.h) offering the Duha (forenoon prayer). She said, “On the day of the conquest of Mecca, the Prophet took a bath in my house and offered eight Rakat. I never saw him praying such a light prayer but he performed perfect prostration and bowing. Narrated ‘Abdullah bin amir that his father had told him that he had seen the Prophet (p.b.u.h) praying Nawafil at night on the back of his Mount on a journey, facing whatever direction it took.