Genesis 22:10-13

And Abraham stretched forth his hand and took the knife to slay his son. ¶ Then the angel of the LORD called unto him out of heaven and said, Abraham, Abraham; and he said, Here am I. And he said, Lay not thine hand upon the lad, neither do thou anything unto him; for now I know that thou doest fear God, seeing thou hast not withheld thy son, thine only son from me. And Abraham lifted up his eyes and looked and beheld behind him a ram caught in a thicket by his horns; and Abraham went and took the ram and offered him up for a burnt offering instead of his son.