Genesis 22:10-12

10: And Abraham stretched forth his hand, and took the knife to slay his son.
11: And the angel of the LORD called unto him out of heaven, and said, Abraham, Abraham: and he said, Here am I.
12: And he said, Lay not thine hand upon the lad, neither do thou any thing unto him: for now I know that thou fearest God, seeing thou hast not withheld thy son, thine only son from me.