 Walking between the two mountains seven times, 4 times from Safa to Marwah and 3 times from Marwah interchangeably, is considered a mandatory pillar ("rukn") of 'Umrah.The Hajj pilgrimage, also called the greater pilgrimage, attracts millions of Muslims from all over the world and almost triples Makkah's population for one week in the twelfth and final Islamic month of "Dhu al-Hijjah".In 2019, the Hajj attracted 2,489,406 pilgrims to the holy city.