2 Corinthians 3:2-4

You are our letter [of recommendation], written in our hearts, recognized and read by everyone. 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. [Ex 24:12; 31:18; 32:15, 16; Jer 31:33] Such is the confidence and steadfast reliance and absolute trust that we have through Christ toward God.