Paul names three things that he was ordained by Christ to do. First, he was ordained a preacher.
Every believer must understand the inerrancy of the inspired word of God. It is given by God. It has no mistakes; it is God breathed; it is just what God intended. The Spirit of God mysteriously uses the human styles of different authors, but what emerges on the page is what God intended. Every word is true, every promise shall stand, every fact is certain. This is the yardstick for everything. We prove everything from Scripture. It tells us the way to heaven; it tells us how to run the church; it tells us how to behave; it tells us about the Lord and about heaven and God's purposes and eternity. Truth is the foundation for all.
Paul did not appoint himself and we do not appoint ourselves. We don't decide we are going to be preachers; indeed we don't appoint ourselves to anything in the church of Jesus Christ. Forget about preachers for the moment. One day you suddenly have an idea. You are a Christian man, a Christian woman, and you think to yourself, I know what I'll do, I'll go into business, I'll open a shop. You say, I rather like animals and I'll do that, and you don't pray about it; you don't think about it; you don't consider the will of God. You say, yes I would enjoy doing that. As Christians we may have ideas and they may be good ones, but then we pray about them and we want to put ourselves in the hand of the Lord, and we are very anxious to follow the rules of guidance in the Scripture. God guides his people and appoints his people. We don't do the first thing that comes into our heads.
They say there are apostles today. No, there are not apostles today. There were only apostles in New Testament times and there were only thirteen: the twelve plus Paul; that is all. In fact Paul had a lot of difficulty establishing that he was an apostle even though God authenticated him with signs and wonders and mighty deeds. The church of Jesus Christ was so clear on the fact that only the twelve were apostles that Paul had quite a lot of difficulty establishing his credentials. Even though he was not one of the twelve, he was a true apostle. He was called by God; he saw the risen Lord in a vision coming to him, and he was enabled to do miracles, and he was a channel of revelation. But because he was not one of the twelve he had a lot of difficulty establishing his credentials. That is why there is this strange term here ‘Whereunto I am ordained a preacher, and an apostle, (I speak the truth in Christ, and lie not).’ Almost always when Paul speaks of himself as an apostle he has to emphasize this in some way, because it was only the twelve plus Paul. Now people say there are apostles today