1 Corinthians 9:1 & 2
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.
Paul begins this section of his letter with some questions and a very obvious answer. Throughout Paul's ministry, there were those who denied his apostleship and here he reminds the readers about the qualifications for being called an apostle. He first asks the question of whether he physically saw Jesus or not and the obvious answer is yes as there were witnesses to his experience on the road to Damascus. He also points out the fact that the readers of this letter are the fruit from his ministry as an apostle. There are many today who give themselves the title of apostle and there are many schools who will sell you a supposed degree to be called an apostle but they have no basis in Scripture. An apostle is one who had Jesus physically appear to them and commission them for His work. There is evidence of this commission in the fruit of that ministry.