9 But thou shalt surely kill him. He would not that every one should privately execute vengeance without a public trial; but he referred to the ordinary custom, that the witnesses should throw the first stone at condemned criminals, as we shall see elsewhere. For it was an admirable provision, that God would have those who had denounced the crime, to be the executors of its punishment, in order that they should be more cautious and moderate in giving their testimony. The reason, which is added at the end, “because he hath sought to thrust thee away from the Lord thy God, who brought thee out, ” etc., again exaggerates the crime on the score of its ingratitude; which was detestable in proportion to the inestimable blessing of their deliverance. It was an act of gross wickedness to rebel against God after they had known Him; but it was still more gross to undervalue their Deliverer. Finally, the advantage and fruit of this severity is subjoined; for, whilst punishment was inflicted on one man’s crime, all others were inspired with terror; and thus the death of one is a wholesome discipline for all, in the way of example.