From The National Geographic:
Stealing a last, long-lashed glance at a camera in Islamabad, Pakistan, yesterday, a camel sold for slaughter waits to be loaded onto a truck. Purchased for the equivalent of nearly a thousand U.S. dollars, the animal was one of many sheep, goats, camels, and cows sacrificed around the world during Id al-Adha, the annual three-day Muslim festival of sacrifice.
The sacrifices commemorate the story of Ibraham (Abraham) and his son, wherein Allah (God) tested Ibrahim by telling him to sacrifice the child, then allowed Ibrahim to sacrifice a ram instead. Muslim families are encouraged to keep a third of the resulting meat for themselves. Another third is to go to the needy, and the final third to friends and neighbors.
More here.