Acts 1:26
And they gave forth their lots; and the lot fell upon Matthias; and he was numbered with the eleven apostles.
From the earliest centuries of this era since Christ, the question has often come up as to whether Matthias was rightly chosen as one of the 12 or whether Paul was the one who should have had that place. The reason that the question comes up is that they do not know the Scriptures.
Those who have read Chapter 15 of Acts can very readily see that Two Gospels were in order and that Paul had one and the 12 (including Matthias) had the other. Paul rehearses the proceedings of that council in Gal. 2:1-10. To him and those with him was entrusted the Gospel of the uncircumcision, and the 12 retained the Gospel of the circumcision.
If Paul had ever been the one who should take the place of Judas, you would think that he would have some knowledge of it. But we find him all the time magnifying his office as an Apostle to the Gentiles. He speaks of the 12 (1 Cor. 15:5) and then mentions why he was disqualified to be one of the 12 apostles. He had not seen Christ when He dwelt among men in the flesh, and he was a persecutor of the Christians.
In Acts 1:15-26, we find the account of the choosing of one to fill the place of Judas. You will note that there were certain qualifications, that he must have been among the number from the baptism of John to the ascension of Christ. Out of the 120 present, only two could qualify; Matthias and Barsabas. Paul was not present, and neither could he have met these requirements, as noted above.
So then, if Paul should have been chosen, he himself would have been a false witness to the facts. Also, Luke recorded that the 11 chose Matthias according to the custom of the Jews and under the direction of the Holy Spirit and that he was numbered with the eleven.
Those who do not know the Scriptures do not realize that Paul was being trained and accredited during the last half of Acts for a ministry that none of the 12 could ever fulfill. The 12 were confined to a ministry to Israel. They were to occupy thrones or places of authority during The Kingdom and preach to the Gentiles then. But that was in connection with The Kingdom, not The Church.
Since the 12 will have their names in the 12 Foundations of the wall of the New Jerusalem (Rev 21:14), and this city will be on the earth, they can have no part in The Church, which is blessed with all spiritual blessings in The Heavenlies and has its citizenship there. And so we must conclude that if Paul should have been one of the 12, he then could never have been The Apostle who proclaimed the Dispensation of The Mystery.
Paul was an apostle, and there is no doubt about that. But the ascended Christ chose him as a gift to The Church, not The Kingdom (Eph 4:11). In Gal 1:1, Paul recognizes that his apostleship was not of men. So he was not chosen by the 11, nor could he have been and retained that claim. His Gospel was not that of the 12 (Gal 1:11). Neither his field of endeavor, but among the heathen (Gal 1:16).