Do we begin again to commend ourselves? Or need we, as some others, epistles of commendation to you, or letters of commendation from you?  Ye are our epistle written in our hearts, known and read of all men:  forasmuch as ye are manifestly declared to be the 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 fleshy tables of the heart.  And such trust have we through Christ to God-ward: not that we are sufficient of ourselves to think any thing as of ourselves; but our sufficiency is of God; who also hath made us able ministers of the new testament; not of the letter, but of the Spirit: for the letter killeth, but the Spirit giveth life.
2 Corinthians 3:1-6