Musnad Ahmad 27:49

Isma'il narrated to us, Ayyub narrated to us, from Nafi', from Ibn 'Umar, who said: When the Messenger of Allah (peace and blessings of Allah be upon him) would return from Hajj, a military expedition, or 'Umrah, and he would ascend a high piece of land or a hill, he would say: "Allah is the Greatest, Allah is the Greatest. There is no god but Allah alone, He has no partner. To Him belongs the dominion, and to Him belongs all praise, and He is capable of all things. We are returning, repenting, prostrating, worshipping, and praising our Lord. Allah has fulfilled His promise, granted victory to His servant, and defeated the confederates alone."