Theophylact of Ohrid — on 2Cor 3:6 (Commentary on 2 Corinthians)

“Our strength, he says, is from God: He made us "sufficient," that is, He strengthened us, made us capable of serving this great divine work — the New Testament. And the Old Law is spiritual, that is, given by the Spirit; but it did not bestow the Spirit, as the New will bestow Him. So the meaning of the words is this: we have been entrusted to impart not the letter, as Moses did, but the Spirit. For the apostles not only taught spiritual and divine things, but also imparted the Spirit through the laying on of hands. The Law, he says, subjects to punishment when it notices someone sinning even in what would seem the very least matter, such as gathering wood on the Sabbath (Num. 15:32–36), while the Holy Spirit, receiving those who have committed innumerable iniquities, justifies them in the bath of baptism and gives life to those dead through sin.”