Musnad Ahmad 27:846

'Abd al-Rahman narrated to us, Malik narrated to us, from Nafi', from Ibn 'Umar, that the Prophet (peace and blessings of Allah be upon him), when he returned from Hajj, 'Umrah, or a military expedition, would say the Takbir (Allahu Akbar) three times upon every high point of the land. Then he would say: "There is no god but Allah alone, He has no partner. To Him belongs the dominion, and to Him belongs the praise, and He is capable of all things. We are returning, repenting, prostrating, worshipping, and praising our Lord. Allah fulfilled His promise, aided His servant, and defeated the confederates alone."