“You yourselves are our letter of recommendation … written not with ink but with the Spirit of the living God, not on tablets of stone but on tablets of human hearts” (v2-3). Paul didn’t need an official “letter of recommendation” authorizing him to be a minister of the gospel. The Corinthian believers were the proof that the message about Jesus, delivered by Paul, had power to change lives. This “new covenant” (v6) didn’t have a capital city or stone tablets; it was based on the living Jesus present in peoples’ hearts.
“Such is the confidence that we have through Christ toward God” (v4). Our confidence is based on the reality of Christ in us, His Spirit bringing new life.