Muslim pilgrims pray around the holy Kaaba during their final circling at the Grand Mosque during the annual hajj pilgrimage for this year in Mecca October 6, 2014Reuters

Haj (Hajj), the annual five-day pilgrimage to Mecca, will begin on Saturday, Sept. 10. Millions of Muslims from across the world attend one of the largest annual gatherings in Mecca every year.

Haj authorities in Saudi Arabia declared the dates of the pilgrimage on Sept. 1 based on the sighting of the moon, Al Jazeera reported. The five-day annual pilgrimage begins on the eighth day of the Islamic month Dhu al-Hijjah, which is the last month of the Islamic calendar.

When is Eid al-Adha 2016? 

Eid al-Adha, the second most important and holiest festival for Muslims after Eid al-Fitr, falls on the 10th day of Dhu al-Hijjah, i.e. on the third day of Haj pilgrimage. This year, Eid al-Adha will be celebrated on Sept. 12 in most of the countries, while in India, Pakistan and Bangladesh the festival of sacrifice will be celebrated on Sept. 13.

On Saturday, Muslims will stream into Mina ahead of the Arafat Day, which is the ninth day of Dhu al-Hijjah. And on Sunday, i.e. on the Day of Arafat, before noon the pilgrims will travel 20kms from Mina to Mount Arafat outside Mecca, to stand at the site where Prophet Mohammed is believed to have delivered his last sermon.

Last year, as many as 1,372,148 Muslims from across the world attended Haj on the first day and the number increased to around 3 million in the next five days. 

For Muslims, performing Haj is one of the five pillars of Islam and every Muslim is expected to go on Haj once in their lifetime. Haj, which aims to bring Muslims from all over the world together, cleanses their sins and brings them closer to God.