RIYADH, Saudi Arabia – Islam’s holiest site is heaving with pilgrims from around the world, many thousands of whom pray shoulder to shoulder outside Mecca’s Grand Mosque as part of their hajj pilgrimage.

The pilgrimage is one of the ‘Five Pillars of Islam,’ and includes certain rites that pilgrims must perform during the three days.

Saudi Arabia has announced that the Islamic hajj pilgrimage, which attracts around 3 million Muslims worldwide each year, will begin on Thursday.

The kingdom’s High Court, which comprises religious scholars who serve as judges, announced Tuesday that Eid al-Adha celebrations coinciding with the pilgrimage will start on Friday.

Hajj is among the five pillars of Islam and is required of all able-bodied Muslims at least once in their lifetime.

Already some 1.4 million people from 160 countries have arrived in the holy city of Mecca in Saudi Arabia for hajj, which according to Islam traces the steps of prophets such as Muhammad, Abraham and Ishmael.

Hajj is a spiritual experience aimed at fostering closeness to Almighty Allah, the cleansing of sins and a sense of unity and equality among Muslims.