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."
1 Corinthians 1:17
For Christ did not send me to immerse people, but to preach the good news. [Note: Christ specifically commissioned Paul to preach; most of the immersing was done by his attendants]. It was not to be done with words of [human] wisdom, so that the [message of the] cross of Christ would not have its power taken away.
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.
Galatians 4:13-14
But you are aware [I am sure] that when I first came preaching the Gospel [message] to you, I had a physical handicap.
1 Corinthians 1:21
For since, according to God's [true] wisdom, the world did not know about Him through its wisdom, God was pleased to save those who believe [in Christ] through the "foolishness" of the message preached.
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 10:1
Now I Paul, who am humble [when speaking] face to face with you, but bold when I am away from you, urge you by the meekness and gentleness of Christ [Note: This means either Paul was imitating Christ's behavior or that the Corinthians were to do so]:
2 Corinthians 12:5-9
I will boast on behalf of this person, but I will not boast about myself [anymore], except about my weaknesses.