You show that you are a letter from Christ, the result of our ministry, written not with ink but with the Spirit of the living God, not on tablets of stone but on tablets of human hearts. 2 Corinthians 3: 3
If you’ve read the book of Acts lately, you’ll notice that Paul was literally a preaching machine. He was unstoppable. Everywhere he went, people got saved, lives were changed and history was altered. But not everyone was happy with him. Some of the Christians started to question his legitimacy as a preacher of the gospel and it came to a point when they asked him for a letter of recommendation from Jerusalem.
Paul’s answer to his critics was sharp. He didn’t need to produce a letter signed by the Apostolic team in Jerusalem because the lives of the people who were changed by his preaching were proof enough of the legitimacy of his ministry. Why should he carry around in his pocket a piece of paper when the people in the churches he planted carry around with them the signature of the life of Christ?
The text also gives us a glimpse of what a Christian is supposed to look like. Christians are supposed to be walking large-print letters, readable by all men. Our conduct should unmistakably point people to Christ and they should never have to guess if we are Christians or not. Like giant billboard ads, the message of our lives should be visible and readable and plain for everyone to see, not buried below a tiny asterisk.