Augustine of Hippo — on 2Cor 3:6 (LETTER 186, TO PAULINUS)

“Could it be possible that the law is not of God? None but an irreligious man would think that. But, because the law commands by the letter and does not help by the Spirit, whoever listens to the letter of the law in such wise as to think that it is enough for him to know what it commands or forbids, whoever trusts in the strength of his own free will to accomplish it and does not take refuge in faith in order to be assisted in his approach to the Spirit that quickens lest the letter find him guilty and kill him, that man has a zeal of God, but not according to knowledge.”