Acts 7:22
Now Moses was educated according to all the wisdom of the Egyptians and became an accomplished speaker and an effective leader.
1 Corinthians 2:1-4
And when I came to you, brothers, it was not with eloquent words or [superior] wisdom that I proclaimed to you the testimony [or, mystery] about God.
2 Corinthians 10:10
For some people are saying, "Paul's letters are heavy and severe, but in person he is [physically?] weak and his speaking ability is unimpressive."
2 Corinthians 11:6
But even though I am an unpolished speaker, I am not lacking in knowledge. We have made this clear to you in every way.