The annual pilgrimage to Mecca during the month of Dhu al-Hijjah. Approximately two million Muslims worldwide participate annually. Performance of the hajj is one of the five pillars of Islam and all adult Muslims are required to perform it at least once in their lives if they are physically and financially able. Pilgrims dress modestly and simply, proclaiming the equality and humility of all believers before God, regardless of worldly differences in race, nationality, class, age, gender, or culture.