From Pope Benedict’s remarks during First Vespers of the Solemnity of the Holy Apostles Peter & Paul, 28 June 2007:

From his Letters, we know that Paul was far from being a good speaker; on the contrary, he shared with Moses and Jeremiah a lack of oratory skill. “His bodily presence is weak, and his speech of no account” (II Cor 10: 10), his adversaries said of him.