1 Corinthians 15:3-11

For what I received I passed on to you as of first importance: that Christ died for our sins according to the Scriptures,

(v3, NIV)

Christ dying for our sins is of first importance. Paul places it as the most important thing that he ensured that he delivered it to them. Jesus died, was buried and then was raised on the third day. Then Jesus appeared to the disciples and a bunch of different people including Paul. Appearing to Paul was different and at a different time. We learn in Acts 9 that Jesus appeared to Paul (Saul at the time) as he was on his way to Damascus to persecute Christians. This takes place sometime after Jesus appeared to the other disciples.

Last of all, as to one untimely born, he appeared also to me.

(v8, ESV)

Paul was a persecutor of Christians. Somehow, his life was changed and now he is a servant of God. I don't think any of you could match up to Paul's sins. Yet, God was able to save a man like Paul. Clearly, Paul's conversion was nothing short of God's work. There was no indication at all that Paul was moving in that direction. Paul clearly acknowledges this and you can see from what he says that nothing he does is by his efforts.

For I am the least of the apostles and do not even deserve to be called an apostle, because I persecuted the church of God. But by the grace of God I am what I am, and his grace to me was not without effect. No, I worked harder than all of them—yet not I, but the grace of God that was with me. Whether, then, it was I or they, this is what we preach, and this is what you believed.

(v9-11, NIV)

Paul's efforts and who he is, is by the grace of God. Regardless, in the end they preached and those at the Corinthian church believed.