What credentials did Paul's critics say he was lacking?
Paul’s critics, especially the Judaizing Jews, charged that he lacked a badge of authority and letters of commendation. They said he could not claim to have walked with Jesus three years like Peter, James, and John, and they dismissed him as an imposter who had drummed up his apostleship himself.
Les explains that Paul repeatedly had to defend his apostleship, and here in chapter 10 it comes up again. Paul was under constant attack, especially from the Judaizing Jews, who said he was an imposter and had invented his apostleship himself. They pointed out that he had no badge of authority, no letters of commendation, and could not claim to have walked with Jesus for three years like Peter, James, and John. This was something Paul constantly had to overcome, with people asking who he thought he was. Paul, however, says he is somebody and has been commissioned as an apostle to the Gentiles. Later in the chapter, his critics also say his letters are weighty, but his presence is weak.