Hajj refers to a Muslim's pilgrimage to Mecca and is one of the five pillars of Islam. At least once in his or her lifetime, each Muslim is expected to undertake this pilgrimage 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 Quran - "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 pilgrimage 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.