2 Corinthians 3:2-5

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