Dressed in white clothing and in a state of ritual purity, they have come from all over the world to participate in one of Islam's five pillars, an obligation for every Muslim who is physically and financially able to do so.
The faithful begin by circling the Kaaba seven times in a ritual called tawaf. Muslims believe that the Kaaba was built by Abraham and his son Ishmael.
They walk between the hills of Safa and Marwa seven times, to commemorate the struggles of Abraham's second wife, Hagar, who frantically ran from one to the other searching for food and water for her child. Her prayers were answered when baby Ishmael's heel hit the ground and a spring, Zam Zam, miraculously sprang from the desert.
After the stoning, Eid al Adha is celebrated by sacrificing goats or lambs, to recall Abraham's loyalty when he was asked by God to sacrifice his son. A portion of the meat is given to the poor, and male pilgrims often shave their heads after this step.