Galatians 1:1-10, 20-2:5
 Paul, an apostle, (not of men, neither by man, but by Jesus Christ, and God the Father, who raised him from the dead;) And all the brethren which are with me, unto the churches of Galatia: Grace be to you and peace from God the Father, and from our Lord Jesus Christ,
Who gave himself for our sins, that he might deliver us from this
present evil world, according to the will of God and our Father: To whom be glory for ever and ever. Amen. I marvel that ye are so soon removed from him that called you into the grace of Christ unto another gospel: Which is not another; but there be some that trouble you, and would pervert the gospel of Christ.
But though we, or an angel from heaven, preach any other gospel unto
you than that which we have preached unto you, let him be accursed.
As we said before, so say I now again, If any man preach any other
gospel unto you than that ye have received, let him be accursed.
For do I now persuade men, or God? or do I seek to please men? for if I
yet pleased men, I should not be the
servant of Christ. Now the things which I write unto you, behold, before God, I lie not. Afterwards I came into the regions of Syria and Cilicia; And was unknown by face unto the churches of Judaea which were in Christ: But they had heard only, That he which persecuted us in times past now preacheth the faith which once he destroyed. And they glorified God in me. Then fourteen years after I went up again to Jerusalem with Barnabas, and took Titus with me also.
And I went up by revelation, and communicated unto them that gospel
which I preach among the Gentiles, but privately to them which were of
reputation, lest by any means I should run, or had run, in vain. But neither Titus, who was with me, being a Greek, was compelled to be circumcised:
And that because of false brethren unawares brought in, who came in
privily to spy out our liberty which we have in Christ Jesus, that they
might bring us into bondage: To whom we gave place by subjection, no, not for an hour; that the truth of the gospel might continue with you.
St. John Chrysostom in his Commentary on Galatians wrote:
"What then was the offense that roused him? It was grave and momentous, one that was estranging them all from Christ, as he himself says further on, 'Behold, I Paul say to you, that if you receive circumcision, Christ will profit you nothing' (Gal.5:2) and again, 'You who would be justified by the Law, you are fallen away from Grace' (Gal.5:4). What is this then?…Some of the Jews who believed were held down by the prepossessions of Judaism…intoxicated by vainglory. Desirous of obtaining for themselves the dignity of teachers, they came to the Galatians, and taught them that the observance of circumcision, sabbaths, and new moons was necessary, and that Paul in abolishing these was not to be borne. For, they said, Peter and James and John, the chiefs of the Apostles and the companions of Christ, did not forbid them…In face…this was…in concession to weakness in the Jewish believers…but these deceivers…misled the simpler ones, saying that Paul was not to be tolerated, for he was a newcomer…that he was a disciple of the Apostles, but they of Christ; that he was single, but they were many, and pillars of the Church…"
"He writes the Epistle as an answer to these charges…As they disparaged his doctrine, saying it came from men, while that of Peter came from Christ, he immediately addresses himself to this point…For Peter and his brother and John and his brother, He called when walking by the seaside, but Paul after his ascension into heaven (Acts 9:3,4). And just as these did not require a second call, but straightaway left their nets and all that they had and followed Him, so this man at his first vocation pressed vigorously forward, waging, as soon as he was baptized, an implacable war with the Jews. In this respect, he chiefly excelled the other Apostles…Luke declares…'As they ministered to the Lord, and fasted, the Holy Spirit said, 'Separate me Barnabas and Saul' (Acts 13:2). From this passage it is manifest that the power of the Son and Spirit is one, for being commissioned by the Spirit, he says that he was commissioned by Christ. He ascribes indifferently the things of the Spirit to God, and the things of God to the Spirit."
"See here too how exactly he follows the principle of humility. For he says not 'they were amazed at me,' 'they praised me' or 'they were astonished,' but he has shown that all was of grace by saying 'they glorified God in me.'
Regarding v.22, Augustine the Blessed said:
"It should be observed that Jews had believed in Christ not only in Jerusalem, nor were they so few that they had been absorbed into the Gentile churches, but they were so numerous that churches came into being from them."