Muslims around the world will be celebrating Eid al-Adha – one of the two most important festivals in the Muslim calendar – later this month.

The holiday, also known as the Feast of the Sacrifice or the Greater Eid, is distinct from Eid-al-Fitr, which was celebrated in July.

How many Eids are there?

Two. Eid-al-Fitr marks the end of Ramadan, when Muslims worldwide break their month-long fast. The date of Eid-al-Fitr – which is also known as the

Lesser Eid – is determined by the confirmed sighting of the new moon. The date of Eid al-Adha also varies in accordance with the Islamic lunar calendar, falling on the tenth day of Dhu al-Hijjah, the twelfth month. In the UK, USA and Saudi Arabia it is expected to start on Thursday 24 September and last four days, while in south Asian countries such as India and Pakistan it is expected to begin a day later.

Why do Muslims celebrate Eid al-Adha?

The Greater Eid commemorates the willingness of Ibrahim to sacrifice his son Ishmael as an act of obedience to Allah – and Allah’s mercy in putting a lamb in Ishmael’s place at the last moment. “Muslims believe that the very moment Ibrahim raised the knife, God told him to stop, that he had passed the test, and to replace Ishmael with a sacrificial ram,” explains Al Arabiya. Eid also marks the end of Hajj, the annual pilgrimage to Saudi Arabia. 

What does the Hajj involve?

The Hajj is the pilgrimage to Mecca, Islam’s holiest site, and is an integral part of the Muslim faith. According to the Koran, all Muslims who can afford to should make the journey to Saudi Arabia at least once in their lifetime. Every year, at least two million Muslims will make the pilgrimage and stand before the Kaaba, a shrine built by Ibrahim, and pray to Allah. The prophet Muhammad said that a person who performs Hajj properly “will return as a newly born baby [free of all sins]”.

Pilgrims usually fly to Jeddah and then travel by bus to Mecca, where there are two rituals to perform: the lesser pilgrimage or Umrah, and the main pilgrimage or Hajj. Pilgrims are expected to wear special white clothes (also called ihram) and carry out certain rituals. However, Saudi Arabia’s Ministry of Health has recommended that certain groups postpone the performance of the Hajj and Umrah because of the risk of MERS infection. The risk is said to be “low”, but elderly people, those with chronic diseases and immunodeficiency, pregnant women and children are advised to postpone their trip as a precautionary measure.

How is Greater Eid celebrated?

In Muslim countries, Eid al-Adha is a public holiday that involves animal sacrifice, prayers and family gatherings. The day begins with morning prayers, followed by visits to family and friends and the exchange of food and gifts. Muslims are obliged to share food and money with the poor so that they can take part in the celebrations.

Worshippers will slaughter an animal, typically a sheep or a goat, during Greater Eid celebrations as a symbol of Ibrahim’s sacrifice to Allah. The animals have to meet certain standards in order to qualify for sacrifice, Arab News reports. They cannot be ill, blind, visibly lame and emaciated and minimum age restrictions apply.

In Pakistan alone, nearly ten million animals are slaughtered on Eid, the International Business Times reports. In Britain, anyone wishing to sacrifice a sheep has to make arrangements for it to be slaughtered humanely.