Jamieson, Fausset and Brown on Galatians 2:9

9. James--placed first in the oldest manuscripts, even before Peter, as being bishop of Jerusalem, and so presiding at the council (Ac 15:1-29). He was called "the Just," from his strict adherence to the law, and so was especially popular among the Jewish party though he did not fall into their extremes; whereas Peter was somewhat estranged from them through his intercourse with the Gentile Christians. To each apostle was assigned the sphere best suited to his temperament: to James, who was tenacious of the law, the Jerusalem Jews; to Peter, who had opened the door to the Gentiles but who was Judaically disposed, the Jews of the dispersion; to Paul, who, by the miraculous and overwhelming suddenness of his conversion, had the whole current of his early Jewish prejudices turned into an utterly opposite direction, the Gentiles. Not separately and individually, but collectively the apostles together represented Christ, the One Head, in the apostleship. The twelve foundation-stones of various colors are joined together to the one great foundation-stone on which they rest (1Co 3:11; Re 21:14, 19, 20). John had got an intimation in Jesus' lifetime of the admission of the Gentiles (Joh 12:20-24).