Musannaf Ibn Abi Shaybah 15111 — Those who said there is no fixed

It is narrated from Nafi' that when Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) climbed Safa, he would face the Ka'bah, then say Allahu Akbar three times, and then recite this supplication: 'La ilaha illallahu wahdahu la sharika lah, lahul-mulku wa lahul-hamdu, wa huwa 'ala kulli shay'in qadir' (There is no god but Allah alone, He has no partner; His is the dominion and His is the praise, and He has power over all things). He would raise his voice with it, and then supplicate a little. Then he would do the same at Marwah, until he had done this seven times in the seven rounds, so the takbirs came to twenty-one. He would hardly be near finishing before we were already exhausted, even though we were young men.