2 Corinthians 3:3

Being made manifest that ye are an epistle of Christ, ministered by us, written not with ink, but with the Spirit of the living God; not in tables of stone, but in tables that are hearts of flesh.

An epistle of Christ, ministered by us ... is a clarification of "Ye are our epistle" in the preceding verse. Paul's position was the same in this as that of the apostles who passed out the bread when Jesus fed the five thousand, the apostles being not the chef on that occasion but the waiters. So here, Paul wrote the epistle in the sense of preaching the gospel; but the true author was Christ who gave the gospel. Plumptre's explanation is that "Paul had been the amanuensis of that letter; but Christ had been the real writer."[12]

Written not with ink ... This merely forces the conclusion that Paul was using "epistle" in a figurative sense. He was not speaking of any ordinary letter written with ink upon a parchment.

Spirit ... tables ... hearts ... God had written the Decalogue with his finger upon tables of stone; but in the new covenant, of which Paul now began to speak, not God's finger, but God's Spirit did the writing. Note the plural of "hearts," a plain reference to the many Christians at Corinth, and supporting the interpretation that Paul's letter was written upon their hearts, not upon his own. There can be no doubt of Jeremiah's great prophecy of the new covenant (Jeremiah 31:31ff) being in the background of Paul's thoughts in this passage.