What does 2 Corinthians 3:1 mean?

In times past, Paul had enjoyed a close relationship with the Corinthians. He had founded the church in Corinth and led many of them to faith in Christ. Their deep respect for him had diminished, though, over time. Some had pledged their allegiance to other apostles and teachers over him. He had rebuked others involved in various sins and foolish practices.

More recently, the Corinthians stood with Paul, against a man who challenged his authority. Still, Paul felt the need to insist that he and those with him were not dishonest "peddlers" of God's Word (2 Corinthians 2:17). They were truly sent out by God to represent Christ.

Now Paul asks if he and his friends need to commend themselves to the Corinthians again. Do they need new letters of recommendation to or from the Corinthians? It was common practice for traveling teachers or speakers to come with such letters. These were written by themselves or others, to establish their credentials to people who did not know them. Such letters are something like the resumé or CV modern people present to potential audiences and business partners.

Paul is not condemning the use of such letters. Instead, he seems to be asking the Corinthians if he has not already proven himself to them based on their history together. He says in the following verses that they themselves—their growth and character and place in Christ—have become his letter of recommendation to the outside world.