Genesis 22:8-13

8And Abraham said, My son, God will provide himself a lamb for a burnt offering: so they went both of them together. 9And they came to the place which God had told him of; and Abraham built an altar there, and laid the wood in order, and bound Isaac his son, and laid him on the altar upon the wood. 10And Abraham stretched forth his hand, and took the knife to slay his son.

11And the angel of the LORD called to him from heaven, and said, Abraham, Abraham: and he said, Here am I. 12And he said, Lay not thy hand upon the lad, neither do thou any thing to him: for now I know that thou fearest God, seeing thou hast not withheld from me thy son, thy only son . 13And Abraham lifted up his eyes, and looked, and behold behind him a ram caught in a thicket by his horns: and Abraham went and took the ram, and offered him for a burnt offering in the stead of his son.