Genesis 22:9-13

Then they came to the place of which God had told him. And Abraham built an altar there and placed the wood in order; and he bound Isaac his son and laid him on the altar, upon the wood. And Abraham stretched out his hand and took the knife to slay his son. But the Angel of the LORD called to him from heaven and said, “Abraham, Abraham!” So he said, “Here I am.” And He said, “Do not lay your hand on the lad, or do anything to him; for now I know that you fear God, since you have not withheld your son, your only son, from Me.” Then Abraham lifted his eyes and looked, and there behind him was a ram caught in a thicket by its horns. So Abraham went and took the ram, and offered it up for a burnt offering instead of his son.