At least once in his or her lifetime, each Muslim is expected to undertake a pilgrimage to Mecca, the sacred city of Islam. This holy journey is called the hajj in Arabic. While a visit to Mecca is beneficial any time of the year, it must take place during the month of Dhu al-Hijja (the last month of the Islamic year) to fulfill the requirements of the hajj.
As with the sawm (fasting), exceptions are made for those who are physically or financially unable to fulfill this obligation, and one is actually commanded not to make the hajj if to do so would cause hardship for his or her family. However, those unable to go themselves may fulfill their obligation by sending someone in their stead.
The hajj is commanded in the Qur'an - "And pilgrimage to the House is a duty unto God for mankind, for him who can find the way thither" (3:97) - and its rites were established by Muhammad, but Muslim tradition dates it back to Adam and Abraham, who were instructed by angels in the performance of the rites. The hajj was one of the last public acts of worship performed by Muhammad before his death.
In part, the hajj commemorates the stories of Abraham, Hagar and Ishmael and it has been assigned various other meanings throughout the centuries. For many Muslims, one of the most meaningful aspects of the pilgrimmage is the unifying effect of bringing together believers from all over the world to meet and worship together.
Upon arrival at the boundary of Mecca (about six miles from the Ka'ba), pilgrims enter the state of ihram (purity) in which they will remain throughout the hajj. Males entering this pure state don the ihram garments - two white, seamless sheets wrapped around the body - and sandals. This aspect of the rite not only signifies the state of holiness the pilgrims have entered, but it serves to contribute to a sense of equality and unity by removing visual indicators of class, wealth and culture. Requirements for women are less stringent, but they usually dress in white with only faces and hands uncovered. While in the state of ihram, pilgrims must not cut their nails or hair, engage in sexual relations, argue, fight or hunt.
When he or she enters the city of Mecca, the pilgrim first walks around the Ka'ba seven times (the tawaf, or circumambulation) while reciting the talbiya, then kisses or touches the Black Stone in the Ka'ba, prays twice towards the Station of Abraham and the Ka'ba and runs seven times between the small mountains of Safa and Marwa.
The second stage of the hajj takes place between the 8th and 12th days of Dhu al-Hijja, beginning with a sermon (khutba) at the mosque on the 7th day. On the eighth day and night, the pilgrim stays at Mina or Arafat. On the ninth day, the ritual of wuquf ("standing") takes place at the small hill of Jabal al-Rahma in Arafat. The pilgrim then returns to Muzdalifa, a small town within the Meccan boundaries, to stay the night.
The tenth day is Eid al-Adha (The Feast of Sacrifice), a major holiday observed by all Muslims. For those participating in the hajj, the day is spent in Mina, where the pilgrim sacrifices an animal to commemorate Abraham's sacrifice and throws seven small stones at each of three pillars on three consecutive days (the pillars represent sins and devils). The pilgrim then returns to Mecca, where he or she once again performs the tawaf (circumambulation of the Ka'ba). The head is then shaved or the hair is trimmed, which marks the end of the state of ihram.
About 2 million Muslims complete the hajj each year. The government of Saudi Arabia has contributed significant resources to maintain the holy places and manage the crowd of pilgrims. Despite the large numbers seen in Mecca each year, only a small percentage of Muslims have fulfilled the duty. Those who have done so may add the title hajj or hajji to their names.
With such a vast number of people in one place at one time, failures of crowd control and other problems have sometimes led to disaster. Some of the recent tragedies associated with the hajj have included:

• On July 31, 1987, Iranian pilgrims riot, causing the deaths of over 400 people.
• On July 9, 1989, two bombs exploded, killing one pilgrim and wounding another 16. Saudi authorities beheaded 16 Kuwaiti Shiite Muslims for bombings after originally blaming Iranian terrorists.
• On July 2, 1990, a stampede inside a pedestrian tunnel leading to Mecca led to the deaths of 1402 pilgrims.
• In 1994, another stampede killed 270 pilgrims.
• On February 1, 2004, 244 Muslim pilgrims were killed and another 244 injured in a stampede during the stoning of the devil ritual.

Perceived failure to prevent these events, or to react appropriately to them, has led to strong criticism of the Saudi Arabian authorities by Muslims. It should be said that such events are common enough across all religious celebrations. In January 2005, for example, Indian Hindu rituals resulted in a stampede when worshippers outside a shrine learned that their relatives had been crushed after slipping on the coconut milk that had been exploded upon an altar as an offering to the god. We can also remember the funeral of Ayatollah Khomeini, when the frenzy of thousands of mourners reached a dangerous peak and the body fell out of the casket.