What does 2 Corinthians 10:17 mean?

Some in Corinth had apparently begun to succumb to false teachers who bragged about their own skills, wisdom, and worthiness. Those frauds have pointed to Paul's unimpressive personal appearance and lack of dramatic speaking skill as evidence that he was not a genuine representative of Christ.

Paul has written that he will not participate in such a competition. He has no reason to promote himself and down opponents in hopes of winning a popularity contest among the Corinthians. He has already won the only contest that matters: being successful, in God's power, at introducing the Corinthians to Christ and establishing a church there. What would be the point of boasting in himself now?

To further support this, Paul quotes from Jeremiah 9:24, much as he did in an earlier letter to the Corinthians (1 Corinthians 1:31). The Lord said to Jeremiah, "Let him who boasts boast in this, that he understands and knows me, that I am the Lord who practices steadfast love, justice, and righteousness in the earth."

Paul shortens this to, "Let him who boasts boast in the Lord." Paul has certainly presented evidence of his genuineness as an apostle and the falseness of his opponents, but his final boast is always in the Lord and not in himself.