The Muslim Eid al-Adha holiday honors Ibrahim’s willingness to sacrifice his son in submission to God’s command. Under Muslim tradition, that son was Ishmael; under the Judeo-Christian religions, that son was Isaac. Both traditions say an angel intervened to prevent the sacrifice.

The event falls on the 10th day of Dhu al-Hijjah on the Muslim lunar calendar and lasts four days. This year, the holiday begins Monday, one day after the 15th anniversary of the Sept. 11, 2001, terror attacks on New York and Washington.

Eid al-Adha is considered a solemn holiday and translates to Festival of Sacrifice.

Ibrahim (Abraham) left Hagar and Ishmael in Canaan with a limited supply of food and water. When the supplies ran out, Hagar ran up and down two hills to find water but finally collapsed. She prayed for deliverance and a spring popped up at Ishmael’s feet, and according to some accounts that happened because of the intervention by the angel Jibra’il (Gabriel). The site became known as the Zamzam Well. Other accounts have Ibrahim taking his son to Mount Moriah and preparing to cut the youth’s neck before the angel substitutes a ram, a story that more closely mirrors the account in the Bible of Abraham’s willingness to sacrifice Isaac.

Prayers for the holiday are held at the mosque and the men of the community are expected to attend after bathing and dressing up. Whether women participate varies among communities. Some travel to Mecca, Saudi Arabia, to perform the hajj.

Affluent Muslims are expected to sacrifice their best halal animals to symbolize Ibrahim’s sacrifice. A third of the animal’s meat is then distributed to the poor with the rest distributed to family and friends.

eid A man carries a sheep prior to Eid al-Adha celebrations in the rebel held Douma neighbourhood of Damascus, Syria, Sept. 11, 2016. Photo: Bassam Khabieh/Reuters

The holiday sparked huge celebrations in the Muslim world with scores of tourists pouring into Gulf Cooperation Council Countries and more than 1 million travelers expected to pass through Dubai International Airport, Gulf News reported.

In Lebanon, the army increased security Sunday, the Daily Star reported.

“The army will apply exceptional security measures around places of worship, main roads, shopping centers, public institutions and tourist sites to reassure citizens and guarantee public safety,” the army said in a statement.

In Iraq, the Islamic State group said it will flog and imprison anyone who celebrates the holiday before Tuesday in Mosul, Iraqi News reported.