Scientists have predicted which years could be the most dangerous for worshippers.
Muslims must perform their prayers five times a day in the direction of the qibla, facing the Kaaba, the building at the center of Islam's holiest mosque in the Saudi Arabian city of Mecca.
The most common and basic greeting during the holiday is "Eid mubarak," which means "blessed Eid" or "have a blessed holiday."
More than 2.37 million pilgrims—mostly from outside Saudi Arabia—are taking part in the five-day ritual.
The world's 1.8 billion Muslim adherents will celebrate Eid al-Adha this week, marking one of Islam's most important holidays.
Health workers have come up with a savvy strategy for combating infectious diseases in conflict-ridden countries.
Iran's Ayatollah Ali Khamenei said Mecca "belongs to all Muslims," and their security during Hajj was a God-given right that Saudi Arabia fails to uphold.
The followers of Amadou Bamba, who believe in the value of hard work and nonviolence, gather each year in West Africa to celebrate their mysterious founder.
Saudi Arabia wants to build a futuristic retractable roof over Mecca.
Syrian President Bashar al-Assad, his opposition, U.S.-backed Kurdish forces and the Islamic State militant group (ISIS) all recognized Eid al-Adha.
Mounting tensions between Qatar and its neighbors spilled over in June, when Saudi Arabia, Egypt, the United Arab Emirates and Bahrain all cut diplomatic ties with Qatar.
The Kaaba, meaning "cube" in Arabic, has been the center of Islam since the time of Prophet Muhammad, but it was worshipped for centuries prior.
Qatar has accused Saudi Arabia of deliberately making it difficult for its pilgrims to obtain permits to go to Mecca.
Seven of the Boeing 777s will fly Qatari pilgrims from Doha to Jeddah to attend the annual Hajj pilgrimage.
Saudi Arabia's foreign minister says Qatar asked his country to cede control of Islam's two holiest sites, but Qatar denies doing so.
Saudi Arabia called the attack "a desperate attempt by Shiite Houthi rebels to disrupt Hajj."
Almost 300 Nigerian pilgrims died in the 2015 stampede in Saudi Arabia.