Once a year, large numbers of Muslim pilgrims converging on Saudi Arabia unite in religious rituals and acts of worship as they perform the Hajj, one of the pillars of Islam. They fulfill a religious obligation, immersing themselves in what can be a spiritual experience of a lifetime for them and a chance to seek God’s forgiveness and the erasure of past sins. Here’s a look at the pilgrimage and its significance to Muslims. What is the Hajj?