2 Corinthians 3:1-3

Are we beginning to commend ourselves again? Or do we need, as some, letters of commendation to you or from you? You are our letter, written in our hearts, known and read by all men; being manifested that you are a letter of Christ, cared for by us, written not with ink but with the Spirit of the living God, not on tablets of stone but on tablets of human hearts.