1 Corinthians 15:1-11 (CSB)

Now I want to make clear for you, brothers and sisters, the gospel I preached to you, which you received, on which you have taken your stand and by which you are being saved, if you hold to the message I preached to you—unless you believed in vain. For I passed on to you as most important what I also received: that Christ died for our sins according to the Scriptures, that he was buried, that he was raised on the third day according to the Scriptures, and that he appeared to Cephas, then to the Twelve. Then he appeared to over five hundred brothers and sisters at one time; most of them are still alive, but some have fallen asleep. Then he appeared to James, then to all the apostles. Last of all, as to one born at the wrong time,[a] he also appeared to me.

For I am the least of the apostles, not worthy to be called an apostle, because I persecuted the church of God. 10 But by the grace of God I am what I am, and his grace toward me was not in vain. On the contrary, I worked harder than any of them, yet not I, but the grace of God that was with me. 11 Whether, then, it is I or they, so we proclaim and so you have believed.