This is also known as Qurbani or sacrifice. It is Wajib upon all mature Muslims who, on the day of `Eid al-Azha, possess Nisab. Whoever qualifies for this is required to purchase a sheep or goat of more than one year in age and cow is two years, and slaughter that in the name of Allah after the `Eid prayer preferably on the same day. The sacrifice can also be done on the two days after Eid. If one fails to make the sacrifice in these three days he will still have to donate the value of the animal (this remains Wajib).