We all know when the first twelve apostles became apostles, at least Catholics do. Not sure about Protestants because they reject early Church Father’s writings, for the most part. And we know that Judas killed himself, and that Matthias became his replacement when the apostles laid their hands on him.
But few people realize when, exactly, Paul became an apostle. He became a disciple on the road to Damascus, when he was stricken down on the road. Annanias led him deeper, to see more. But Paul tells us, starting at Galatians 1:15 and following:
God, who had specially chosen me while I was still in my mother’s womb, called me through his grace and chose to reveal his Son in me, so that I might preach the Good News about him to the pagans. I did not stop to discuss this with any human being, nor did I go up to Jerusalem to see those who were already apostles before me, but I went off to Arabia at once and later went straight back from there to Damascus. Even when after three years I went up to Jerusalem to visit Cephas and stayed with him for fifteen days, I did not see any of the other apostles; I only saw James, the brother of the Lord, and I swear before God that what I have just written is the literal truth. After that I went to Syria and Cilicia, and was still not known by sight to the churches of Christ in Judaea, who had heard nothing except that their one-time persecutor was now preaching the faith he had previously tried to destroy; and they gave glory to God for me.It was not till fourteen years had passed that I went up to Jerusalem again. I went with Barnabas and took Titus with me. I went there as the result of a revelation, and privately I laid before the leading men the Good News as I proclaim it among the pagans; I did so for fear the course I was adopting or had already adopted would not be allowed. And what happened? Even though Titus who had come with me is a Greek, he was not obliged to be circumcised. The question came up only because some who do not really belong to the brotherhood have furtively crept in to spy on the liberty we enjoy in Christ Jesus, and want to reduce us all to slavery. I was so determined to safeguard for you the true meaning of the Good News, that I refused even out of deference to yield to such people for one moment. As a result, these people who are acknowledged leaders – not that their importance matters to me, since God has no favourites – these leaders, as I say, had nothing to add to the Good News as I preach it. On the contrary, they recognised that I had been commissioned to preach the Good News to the uncircumcised just as Peter had been commissioned to preach it to the circumcised. The same person whose action had made Peter the apostle of the circumcised had given me a similar mission to the pagans. So, James, Cephas and John, these leaders, these pillars, shook hands with Barnabas and me as a sign of partnership: we were to go to the pagans and they to the circumcised. The only thing they insisted on was that we should remember to help the poor, as indeed I was anxious to do.
So Paul did not become an apostle for 15 years after his conversion. And he had to prove himself to the other apostles in order to be welcomed into the brotherhood of apostles. He went obediently to those who learned from Christ himself, and laid out his curriculum to be approved. What gave them the authority to approve or disapprove it? The Holy Spirit did this, as promised by Jesus, when the universal Church was born on Pentecost. (Remember, Paul didn’t have the commission to preach yet, so he wanted to be sure he was preaching correctly.) So as a result of rebuking false teachers and defending the true faith against them, the leaders of the Church, Peter, James and John, laid hands on Paul and gave him the gift of the Holy Spirit, which protected him from preaching error the remainder of his time on earth.
The feast today proves the inerrancy on the apostles, which by laying on of hands is passed on to their successors, who are the bishops of the Catholic Church. Remember that it takes a bishop to proclaim a bishop.