The word eid is derived from aud meaning to return. In Islam, it means a recurring happiness. The word adha, the plural of adhat means a sacrifice. On this occasion, all the Muslims who can afford, sacrifice an animal. In the case of a goat or a sheep, one animal is suffices for one household. In the case of a cow or a camel, seven men may be partners. It may be sacrificed on the day of Eid or during the two or three days that follows, called the tashriq days. The animal sacrificed must be free from apparent physical defects, and full-grown (musinna). The goat or sheep should be a year old, the cow two years and the camel five. The skin of the animal must, however, be disposed of in charity. 

The Eid al-Adha is commemorative of that unparalleled act of devotion of that noble soul, Abraham who in obedience to the command of his Lord, readily offered the life of his beloved son, Ismael. In Islam, this act of sacrifice is the symbol of a Muslim's readiness to lay down his life, and to sacrifice all his interests and desires in the cause of truth. The purpose of sacrifice is not fulfilled only by shedding the blood of an animal, but it is really fulfilled when a man submits himself completely and readily to the command of God. Fakhruddin Razi writes in Tafsir al-Kabir (6:183) that, "The man who offers the sacrifice should keep this fact uppermost in his mind that the most important motive behind this is the willing submission to God." Islam has not only shaken the idea of human sacrifice root and branch, but has completely ended all such inhuman practices, which were very common with the people before Islam. The Koran makes a pointed reference to the fact that this sacrifice of animals is commemorative of Abraham's offer of his son's life at the command of God, which was substituted by a ram, and it has been perpetuated by Islam. It is related that once the Companions of the Prophet asked him about this sacrifice, he replied: "This is commemorative of the Sunnah of your father Abraham" (Tafsir Ibn Kathir, 3:221).