Are we beginning to commend ourselves again? Or do we need, as some do, letters of recommendation to you, or from you? You yourselves are our letter of recommendation, written on your hearts, to be known and read by all men; and you show that you are a letter from Christ delivered 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.
Such is the confidence that we have through Christ toward God. Not that we are competent of ourselves to claim anything as coming from us; our competence is from God, who has made us competent to be ministers of a new covenant, not in a written code but in the Spirit; for the written code kills, but the Spirit gives life.
–2 Corinthians 3:1-6