For I speak to you Gentiles - What I am saying respecting the Jews, I say with reference to you who are Gentiles, to show you in what manner you have been admitted to the privileges of the people of God; to excite your gratitude; to warn you against abusing those mercies. etc. As Paul also was appointed to preach to them, he had a right to speak to them with authority.
I am the apostle of the Gentiles - The apostle of the Gentiles, not because other apostles did not preach to Gentiles, for they all did, except perhaps James; nor because Paul did not himself preach occasionally among the Jews; but because he was especially called to carry the gospel to the Gentiles, and that this was his original commission Acts 9:15; because he was principally employed in collecting and organizing churches in pagan lands; and because the charge of the Gentile churches was especially intrusted to him, while that of the Jewish churches was especially intrusted to Peter; see Galatians 1:16; Ephesians 3:8; Galatians 2:7-8. As Paul was especially appointed to this function, he claimed special authority to address those who were gathered into the Christian church from pagan lands.
I magnify mine office - I honor δοξάζω doxazō my ministry. I esteem it of great importance; and by thus showing that the gospel is to be preached to the Gentiles, that the barrier between them and the Jews is to be broken down, that the gospel may be preached to all people, I show that the office which proclaims this is one of signal honor. A minister may not magnify himself, but he may magnify his office. He may esteem himself as less than the least of all saints, and unworthy to be called a servant of God Ephesians 3:8, yet he may feel that he is an ambassador of Christ, intrusted with a message of salvation, entitled to the respect due to an ambassador, and to the honor which is appropriate to a messenger of God To unite these two things constitutes the dignity of the Christian ministry.