Cosmas Indicopleustes — on 2Cor 3:6 (The Christian Topography, Book 7)

“He made them, as Paul writes, sufficient as ministers of a new covenant, not of the letter, but of the spirit: for the letter killeth but the spirit giveth life; as if he said: We have been made sufficient by God by means of signs and of the Holy Spirit, while teaching such things, to persuade those who hear us; for God hath appointed us ministers of the new and life-giving covenant, not of the old letter, that is, of the written law which threatens death, but of the life-giving power, that is, of the Holy Spirit.”