1Cor 9:1-3 Am I not free? Am I not an apostle? Have I not seen Jesus our Lord? Are you not the result of my work in the Lord? Even though I may not be an apostle to others, surely I am to you! For you are the seal of my apostleship in the Lord. This is my defense to those who sit in judgment on me.
In this chapter Paul affirms and reliquishes his rights and entitlements as a minster of the gospel. Here he affirms his calling, as he says in all of his letters: "Paul, called to be an apostle of Christ Jesus by the will of God" 1Cor 1:1 As an apostle he was free from accountability to other men. He had seen the Lord on the road to Damascus as also was affirmed by Ananias saying, "Brother Saul, the Lord— Jesus, who appeared to you on the road as you were coming here— has sent me so that you may see again and be filled with the Holy Spirit." Acts 9:17 And the Lord said to Paul "Now get up and stand on your feet. I have appeared to you to appoint you as a servant and as a witness of what you have seen of me and what I will show you. I will rescue you from your own people and from the Gentiles. I am sending you to them to open their eyes and turn them from darkness to light, and from the power of Satan to God, so that they may receive forgiveness of sins and a place among those who are sanctified by faith in me." Acts 26:16-18 Paul not only had the endorsement and commission of Jesus Christ, but in saying "what I will show you", the Lord indicated that he would be giving Paul personal revelation. the basis of which we accept Paul's word as scripture. Thus he also acknowledges in saying to the Thessalonians, "when you received the word of God, which you heard from us, you accepted it not as the word of men, but as it actually is, the word of God, which is at work in you who believe." 1Th 2:13 And the apostle Peter in 2Peter 3:16 likewise says that Paul's writings are scripture.
While the above is unique to the apostles, his final defense is something which all ministers of the gospel may use to affirm their calling. Namely, what impact has your ministry had on others? Jesus said, "Watch out for false prophets. They come to you in sheep's clothing, but inwardly they are ferocious wolves. By their fruit you will recognize them."Mt 7:15,16 The Corinthians along with his other churches are themselves evidence of his calling. Jesus said, "This is to my Father's glory, that you bear much fruit, showing yourselves to be my disciples." John 15:8