Eid al-Adha 'Feast of the Sacrifice', IPA: [?i?d æl???d??æ?]) or Eid Qurban (Persian: ??? ??????), also called the "Festival of the Sacrifice", is the second of two Islamic holidays celebrated worldwide each year (the other being Eid al-Fitr), and considered the holier of the two.
It honours the willingness of Ibrahim (Abraham) to sacrifice his son as an act of obedience to God's command. But, before Abraham could sacrifice his son, God provided a lamb to sacrifice instead. In commemoration of this intervention, an animal is sacrificed and divided into three parts. One share is given to the poor and needy, another is kept for home, and the third is given to relatives.
One of the main trials of Ibrahim (Abraham's) life was to face the command of God to sacrifice his dearest possession, his son. The son is not named in the Quran, but the earliest Islamic traditions identify Isma'il (Ishmael) as the son who was sacrificed. Upon hearing this command, Abraham prepared to submit to the will of God. During this preparation, Shaytaan (the Devil) tempted Abraham and his family by trying to dissuade them from carrying out God's commandment, and Abraham drove Satan away by throwing pebbles at him. In commemoration of their rejection of Satan, stones are thrown at symbolic pillars during the Stoning of the Devil during Hajj rites.
When Abraham attempted to cut his son's throat on mount Arafat, he was astonished to see that his son was unharmed and instead, he found an animal  which was slaughtered. Abraham had passed the test by his willingness to carry out God's command.
100 "O my Lord! Grant me a righteous (son)!"
101 So We gave him the good news of a boy ready to suffer and forbear.
102 Then, when (the son) reached (the age of) (serious) work with him, he said: "O my son! I see in vision that I offer thee in sacrifice: Now see what is thy view!" (The son) said: "O my father! Do as thou art commanded: thou will find me if Allah so wills one practicing Patience and Constancy!"
103 So when they had both submitted their wills (to Allah), and he had laid him prostrate on his forehead (for sacrifice),
104 We called out to him "O Abraham!
105 "Thou hast already fulfilled the vision!" – thus indeed do We reward those who do right.
106 For this was obviously a trial–
107 And We ransomed him with a momentous sacrifice:
108 And We left (this blessing) for him among generations (to come) in later times:
109 "Peace and salutation to Abraham!"
110 Thus indeed do We reward those who do right.
111 For he was one of our believing Servants.
112 And We gave him the good news of Isaac – a prophet – one of the Righteous.
Abraham had shown that his love for God superseded all others: that he would lay down his own life or the lives of those dearest to him in submission to God's command. Muslims commemorate this ultimate act of sacrifice every year during Eid al-Adha. While Abraham was prepared to make an ultimate sacrifice, God ultimately prevents the sacrifice, additionally signifying that one should never sacrifice a human life, especially not in the name of God.