Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) said that when the Messenger of Allah (peace and blessings be upon him) returned from a military expedition, Hajj or Umrah, he would say 'Allahu Akbar' (Allah is the Greatest) three times at every high place, then say: "'La ilaha illallahu wahdahu la sharika lah, lahul-mulku wa lahul-hamd, wa huwa 'ala kulli shay'in qadir, ayibuna ta'ibuna 'abiduna sajiduna li-rabbina hamidun, sadaqallahu wa'dah, wa nasara 'abdah, wa hazamal-ahzaba wahdah' (There is no god but Allah, alone, without partner; His is the dominion and His is the praise, and He is capable of all things. Returning, repenting, worshipping, prostrating, praising our Lord. Allah fulfilled His promise, helped His servant, and alone defeated the confederates)."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 10364