Sahih Muslim Book 4, Hadith Number 1554.

Chapter : Excellence of observing two Rak’ahs in the mosque for one who comes back from a journey.

‘Abdullah b. Harith b. Naufal reported: I had been asking about, as I was desirous to find one among people who should inform me, whether the Messenger of Allah (may peace be upon him) observed the forenoon prayer, but I found none to narrate that to me except Umm Hani, daughter of Abu Talib (the real sister of Hadrat ‘Ali), who told me that on the day of the Conquest the Messenger of Allah (may peace be upon him) came (to our house) after the dawn had (sufficiently) arisen. A cloth was brought and privacy was provided for him (the Holy Prophet). He took a bath and then stood up and observed eight rak’ahs. I do not know whether his Qiyam (standing posture) was longer, or bending or prostration or all of them were of equal duration. She (Umm Hani) further said: I never saw him saying this Nafl prayer prior to it or subsequently. (Al-Muradi narrated on the authority of Yunus that he made no mention of the words: “He informed me.”)