In these verses,
I. The apostle makes an apology for seeming to commend himself. He thought it convenient to protest his sincerity to them, because there were some at Corinth who endeavoured to blast his reputation; yet he was not desirous of vain-glory. And he tells them, 1. That he neither needed nor desired any verbal commendation to them, nor letters testimonial from them, as some others did, meaning the false apostles or teachers, 2 Corinthians 3:1. His ministry among them had, without controversy, been truly great and honourable, how little soever his person was in reality, or how contemptible soever some would have him thought to be. 2. The Corinthians themselves were his real commendation, and a good testimonial for him, that God was with him of a truth, that he was sent of God: You are our epistle, 2 Corinthians 3:2. This was the testimonial he most delighted in, and what was most dear to him - they were written in his heart; and this he could appeal to upon occasion, for it was, or might be, known and read of all men. Note, There is nothing more delightful to faithful ministers, nor more to their commendation, than the success of their ministry, evidenced in the hearts and lives of those among whom they labour.
II. The apostle is careful not to assume too much to himself, but to ascribe all the praise to God. Therefore, 1. He says they were the epistle of Christ, 2 Corinthians 3:3. The apostle and others were but instruments, Christ was the author of all the good that was in them. The law of Christ was written in their hearts, and the love of Christ shed abroad in their hearts. This epistle was not written with ink, but with the Spirit of the living God; nor was it written in tables of stone, as the law of God given to Moses, but on the heart; and that heart not a stony one, but a heart of flesh, upon the fleshy (not fleshly, as fleshliness denotes sensuality) tables of the heart, that is, upon hearts that are softened and renewed by divine grace, according to that gracious promise, I will take away the stony heart, and I will give you a heart of flesh, Ezekiel 36:26. This was the good hope the apostle had concerning these Corinthians (2 Corinthians 3:4) that their hearts were like the ark of the covenant, containing the tables of the law and the gospel, written with the finger, that is, by the Spirit, of the living God. 2. He utterly disclaims the taking of any praise to themselves, and ascribes all the glory to God: ldblquote We are not sufficient of ourselves, 2 Corinthians 3:5. We could never have made such good impressions on your hearts, nor upon our own. Such are our weakness and inability that we cannot of ourselves think a good thought, much less raise any good thoughts or affections in other men. All our sufficiency is of God; to him therefore are owing all the praise and glory of that good which is done, and from him we must receive grace and strength to do more.
dblquote This is true concerning ministers and all Christians; the best are no more than what the grace of God makes them. Our hands are not sufficient for us, but our sufficiency is of God; and his grace is sufficient for us, to furnish us for every good word and work