Students of Dar-ul-Ulaoom Jamia Naeemia seminary watch butchers slaughter bulls in Lahore, Pakistan on Oct. 16 as part of the annual festival of Eid-al-Adha, or the Festival of Sacrifice. Muslims across the world are celebrating the holiday, which marks the end of the Hajj pilgrimage to Mecca and commemorates prophet Abraham's proverbial readiness to sacrifice his son to show obedience to God.