The hajj is the annual pilgrimage to Mecca that all Muslims are required to make at least once in life, provided that a person is physically and financially capable. The hajj occurs annually from the eighth to the twelfth day of the month of Dhu al-Hijjah in the Islamic calendar. The hajj consists of a series of rituals that symbolize events in the lives of the prophet Ibrahim (the biblical Abraham) and his wife Hagar. Pilgrims circle the Kaaba seven times; travel seven times between two hills; drink from the Well of Zamzam; pray and stand in vigil on the plain of Mount Arafat; throw seven stones in a ritualized stoning of the Devil; sacrifice an animal or have one sacrificed on their behalf; and celebrate the Eid al-Adha festival, among other things. The hajj was derived from a pre-Islamic pilgrimage to Mecca that Muhammad rededicated to the One God of Islam in 631 CE.
The hajj is one of the Five Pillars of Islam—practices required of all Muslims. Since the beginning of Islam, the pilgrimage has acted as a shared spiritual experience for Muslims across the world and across the centuries. A pilgrim who has completed the Hajj is accorded the honorific title Hajji, or Hajjah for women, as a mark of respect. All pilgrims must enter the sacred state of Ihram by cleansing themselves physically and spiritually in order to begin and complete the hajj. This involves, among other things, wearing a simple prescribed garment to avoid drawing attention to oneself and to show the solidarity of all Muslims in submission to God. Millions of Muslims from across the world travel to Mecca each year to take part in the hajj. Interestingly, a Harvard University study demonstrated that those who make the pilgrimage report increased belief in peace and harmony among ethnic and religious groups over the long term.