Musnad Ahmad 27:270

Yahya narrated to us, from Ubayd Allah, Nafi’ narrated to me, from Ibn Umar, who said: When the Messenger of Allah (peace and blessings of Allah be upon him) would return from military expeditions, or raiding parties, or Hajj, or Umrah, whenever he ascended a mountain pass or a high plateau, he would say the takbir three times, and 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, worshipping, prostrating, to our Lord praising. Allah fulfilled His promise, and aided His servant, and defeated the confederates alone."