Sahih BukhariVolume 5, Book 59, Number 442:

Narrated 'Abdullah:

Whenever Allah's Apostle returned from a Ghazwa, Hajj or 'Umra, he used to start (saying), "Allahu-Akbar," thrice and then he would say, "None has the right to be worshipped except Allah alone Who has no partners. To Him belongs the Kingdom, all praises are for Him, and He is able to do all things (i.e. Omnipotent). We are returning with repentance (to Allah) worshipping, prostrating, and praising our Lord. Allah has fulfilled His Promise, made His Slave victorious, and He (Alone) defeated the clans (of infidels) ."