Around 1.7 million Muslims have gathered this year in the holy city of Mecca in Saudi Arabia for the annual pilgrimage – the hajj. The five-day pilgrimage is a once-in-a-lifetime obligation for all Muslims who have the physical and financial ability to undertake the journey.

So, what is the hajj and what is its spiritual significance?

The fifth pillar

Millions of Muslims from diverse countries such as Indonesia, Russia, India, Cuba, Fiji, the United States, Nigeria and others congregate in Mecca during the last month of the Muslim lunar year.

Pilgrims wear plain, white garments. Men drape seamless, unstitched clothing and women dress in plain white dresses and headscarves. The idea behind dressing simply is to mask any differences in wealth and status.

The pilgrimage is considered the fifth pillar of Islamic practice (the other four being the profession of faith, five daily prayers, charity and the fast of Ramadan). In calling Muslims to perform the hajj, the Quran says,

“Proclaim to men the pilgrimage: they will come to thee on foot and on every lean camel, coming from every remote path.”

The rites of the hajj are believed to retrace events from the lives of prominent prophets such as Ibrahim and Ismail (Abraham and Isaac, as named in the Bible).

The first day of the hajj

Pilgrims start by circling the “Holy Kaaba,” the black, cube-shaped house of God (at the center of the most sacred mosque in Mecca), seven times.

The Kaaba occupies a central place in the lives of Muslims. In all parts of the world, Muslims are expected to turn toward the Kaaba when performing their daily prayers.

Specific rules concerning going around the Kaaba are prescribed for pilgrims. They may also kiss, touch or approach the Kaaba during the pilgrimage as a sign of their respect and continued devotion.

The Quran tells the story of Ibrahim’s sacrifice, who when commanded by God, agreed to sacrifice his son, Ismail. Muslims believe the Kaaba holds the black stone upon which Ibrahim was called to sacrifice Ismail.

In performing the rituals, they join in a long line of pilgrims to Mecca – including Prophet Muhammad – who circled the Kaaba.

Pilgrims then proceed to a ritual walking – about 100 meters from the Kaaba – to hills known as “Safa” and “Marwah.” Here they re-create another significant event recorded in the Quran: when Ibrahim was granted a son by God through his Egyptian slave girl Hajar. After the birth of Ismail, God instructed Ibrahim to take Hajar and her newborn son out into the desert and leave them there. Ibrahim left them near the present-day location of the Kaaba. Ismail cried out with thirst and Hajar ran between two hills, looking for water until she turned to God for help.

God rewarded Hajar for her patience and sent his angel Jibreel to reveal a spring, which today is known as “Zamzam Well.” Pilgrims drink water from the sacred well and may take some home for blessings.

The second day of the hajj

The hajj “climaxes” with a sojourn into the plains of Arafat near Mecca. There, pilgrims gather in tents, spend time with one another and perform prayers. Some pilgrims will ascend a hill known as the “Mount of Mercy,” where Prophet Muhammad delivered the farewell sermon toward the end of his life.

They then proceed to an open plain near Mecca, often a highlight of the journey for many pilgrims. Muslims believe that the spirit of God comes closer to Earth in this place at the time of the pilgrimage.

As a scholar of global Islam, during my fieldwork I have interviewed those who have gone on the hajj. They have described to me their personal experiences.

Many pilgrims, when standing in the plains of Arafat, feel a close communion with God.

Final three days

Afterwards, pilgrims move to Mina, also known as the Tent City, about five kilometers from the holy city of Mecca. Here, they reenact another part of the story of Ibrahim’s test of faith in the sacrifice of his son.

They recall how Satan tried to tempt Ibrahim to disobey God’s call to sacrifice Ismail. Ibrahim, however, remained unmoved and informed Ismail, who was willing to be sacrificed. To reenact Ibrahim’s rebuff of Satan’s temptation, pilgrims throw small stones at a stone pillar.

They then proceed to follow Ibrahim in the act of sacrifice. The Quran says just as Ibrahim attempted to kill his son, God intervened and a ram was sacrificed in place of Ismail. In remembrance, Muslims all over the world sacrifice an animal on this day. The “festival of the sacrifice” is known as Eid al-Adha.

Many pilgrims spend the next few days repeating the stoning at Mina (at least six more times) and going around the Holy Kaaba in Mecca (at least once more). Pilgrims also start to put on their everyday clothes to indicate a transition to their worldly life.

It is believed that a proper performance of the hajj can absolve Muslim pilgrims of any previous sins. However, Muslims also believe that just undertaking the pilgrimage is not enough: It is up to God to judge the pilgrimage as acceptable or not.

Creating one Muslim community

The hajj is a massive organizational project for the Saudi authorities. Issues concerning crowd management, security, traffic and tensions constantly plague the successful organization of the annual event. A deadly stampede in 2015 left over 700 dead.

There are other ongoing tensions as well: Some Shia governments such as Iran, for example, have leveled charges alleging discrimination by Sunni Saudi authorities. Furthermore, this year, citizens of Qatar were not able to perform the hajj following the decision by Saudi Arabia and three other Arab nations to severe diplomatic ties with the country.

To address such issues, many Muslims have called for the Organization of the Islamic Cooperation (OIC), an intergovernmental organization, to put together an international, multi-partisan committee to organize the pilgrimage.

Perhaps that could help avoid regional or sectarian conflicts. The hajj, after all, is any individual Muslim’s single most symbolic ritual act that reflects the ideal of unity.

By requiring Muslims to don the same clothes, pray in the same spaces and perform the same rituals, the hajj creates a global Muslim community, with no class distinctions.

Ken Chitwood does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond the academic appointment above.