Text in red are my additions.
1. And some coming down from Judea, taught the brethren: That except you be circumcised after the manner of Moses, you cannot be saved.
And some coming down, etc. These were Jews who had been converted to Christianity. They contended that circumcision and the observances of the Mosaic Law were essential for salvation, and that therefore converts from paganism should first be subject to these observances. In order to make their influence more effective they came down from Jerusalem, the seat of great authority, to Antioch, which was known as the center of the Church, and whose Christian community was composed of Gentile converts. It is true that the vision of St Peter and the consequent conclusion that Mosaic observances were no longer necessary for salvation (Acts 10-11) were well known, and had been accepted by the faithful at Jerusalem; but as the number of converts, especially from the sect of the Pharisees, grew, the old ideas about the eternity of the Law of Moses and the necessity of its observance again became prominent. The case of Cornelius and the decision of St Peter at the time were gradually looked upon as exceptional, and the result of a special divine intervention.
2. And when Paul and Barnabas had no small contest with them, they determined that Paul and Barnabas, and certain others of the other side, should go up to the apostles and priests in Jerusalem about this question.
The doctrine of those Jewish converts from Jerusalem caused a great controversy and agitation in the Church at Antioch, in particular, since the agitators pretended to have authority from the Apostles at Jerusalem (Gal 2: 2, 6, 9). Hence the heads of the Church at Antioch decided that Paul and Barnabas, with Titus (Gal 2:1). and some others, should go up to Jerusalem and consult Peter and the other Apostles there with a view to settling this question (Gal 2:9).
The ex aliis (“of the other side”) of the Vulgate here would imply that among the delegates sent to Jerusalem there were some opposed to the opinion of Paul; but since the phrase is not in the Greek it is thought that it is a corruption for ex illis (of those). Certain other Latin versions have ex illis instead of ex aliis.
From the Epistle to the Galatians 2:2 we know that St Paul was moved to go up to Jerusalem at this time by divine revelation, as well as by the decision of the elders of the Church of Antioch.
21. For Moses of old time hath in every city them that preach him in the synagogues, where he is read every sabbath.
St James here explains why he counsels the pagan converts to abstain from the foregoing things, namely, because the Mosaic Law which prohibits them has been read in the Synagogues every Saturday from the remotest times, and is, therefore, so well known to the Jews that to see pagan converts openly disregard it would be more than they could peacefully tolerate.
St James, therefore, agrees with St Peter and St Paul that the Gentiles are free from the Mosaic observances which the Jews wish to have imposed on them, but he at the same time counsels the Gentiles to refrain from certain pagan practices which were extremely obnoxious to the Jews. So much was necessary for peace and unity in the Church.
22. Then it pleased the apostles and ancients, with the whole church, to choose men of their own company, and to send to Antioch, with Paul and Barnabas, namely, Judas, who was surnamed Barsabas, and Silas, chief men among the brethren.
The Apostles and priests with the whole assembly now selected from among their group some prominent men of authority to accompany Paul and Barnabas and carry the decree of the Council to the Church at Antioch. Those chosen for this mission were Judas Barsabas, probably a brother of Joseph Barsabas (Acts 1:23), and Silas, in Latin, Silvanus, who was afterwards the constant companion of St. Paul on his missions to Macedonia (Acts 15:40; 16:19; 17:4; 2 Cor 1:19; 1 Thess 1:1; 2 Thess 1:1). Chief men, etc., ανδρας ηγουμενους; i.e., leaders, guides, which shows they were men of special authority, as priests or Bishops.
23. Writing by their hands: The apostles and andents, brethren, to the brethren of the Gentiles that are at Antioch, and in Syria and Cilicia, greeting.
Writing by their hands; i.e., the Apostles wrote letters by them, or employed these men to write for them in the following manner: “The Apostles,” etc. In Greek we have “and” before brethren, but the reading of the Vulgate is according to the best Greek MSS. The mention of ” Syria and Cilicia ” shows that the errors had spread beyond Antioch.
24. Forasmuch as we have heard, that some going out from us have troubled you with words, subverting your souls; to whom we gave no commandment:
25. It hath seemed good to us, being assembled together, to choose out men, and to send them unto you, with our well beloved Barnabas and Paul:
Subverting your souls; i.e., troubling or upsetting their minds by requiring them without authority to submit to the Mosaic observances. Being assembled together; i.e., being assembled in full accord (Greek).
26. Men that have given their lives for the name of our Lord Jesus Christ.
27. We have sent therefore Judas and Silas, who themselves also will, by word of mouth, tell you the same things.
Judas and Silas, who would tell them by word of mouth the selfsame things which were written in the letters they were bearing.
28. For it hath seemed good to the Holy Ghost and to us, to lay no further burden upon you than these necessary things:
29. That you abstain from things sacrificed to idols, and from blood, and from things strangled, and from fornication ; from which things keeping yourselves, you shall do well. Fare ye well.
The prohibitions of the Council of Jerusalem are mentioned three times in the Acts: here, in Acts 15:20, and in Acts 21:25. There are two readings of the decree of this Council: (a) The Three Clause Text or Western Reading—found in Codex Bezae (D), the Old Latin, Irenaeus, Tertullian, etc.,—mentions only three prohibitions,— abstinence from meats offered to idols, from blood, and from fornication. Codex Bezae and Irenaeus add the Golden Rule: “Whatsoever ye would not have done unto yourselves, do ye not unto others.” (b) The Four Clause Text—found in the great uncial MSS., Sinaitic, Alex., Vat., etc.—adds to the three prohibitions just mentioned a fourth, namely, abstinence from things strangled. Which of these readings is correct is a much disputed question. Some think the two can be reconciled by following the reading, “sanguine suffocato,” found in certain MSS. of the Vulgate and in some Latin Fathers.
Guided by the Holy Ghost, according to the promise of Christ (Matt 18:18; John 14:26; 15:26; 16:13), the Apostles gave an infallible decision on the questions under discussion. The pagan converts were to be troubled with “no further burden” from the Law of Moses, except the observance of the Decalogue, which was of the natural law; but, for the sake of unity and peace in the Church, they should refrain from certain pagan practices very offensive to the Jews. The Apostolic decree, then, was partly a food law or disciplinary measure, inasmuch as it commanded a temporary and local abstinence from certain foods prohibited by the Mosaic Law; and partly a moral law, inasmuch as it prohibited fornication. The opinion of Resch, Harnack, and other advocates of the Three Clause Reading—who think the decree was merely a moral enactment, and that it forbade sins against God (idolatry), against self (fornication), and against the neighbor (blood) —is not supported by convincing arguments.
The rationalists find a difficulty here. They say: (a) St. Luke’s account of the decree of the Council of Jerusalem cannot be correct, because St. Paul makes no mention of such a decree when writing to the Galatians. Answer: It was not to St. Paul’s purpose to refer to this decree in his Epistle to the Galatians. He was there writing a defense of himself, and omitted all that did not serve this end. Moreover, the Jewish converts of Galatia, to whom St. Paul wrote his Epistle, held that the Mosaic observances were necessary in order to be perfect Christians, not, however, for salvation. The decree of the Council condemned the teaching that the Mosaic observances were necessary for salvation; (b) St. Paul, writing to the Corinthians (1 Cor 10:25-27), gave them permission to eat meats that had been offered in sacrifice to idols. Answer: The prohibition or counsel to pagan converts not to eat meat offered to idols was only a disciplinary matter for the sake of peace and unity among the newly converted. Accordingly, where the Jews were far in the minority, as at Corinth, it was not necessary to insist on a merely disciplinary part of the decree of the Council of Jerusalem. It was not wrong in itself to eat meat offered to idols. See A. Camerlynck, Com. in Actus. Apost.; W. Drum, S.J., The Apostolic Decree, Eccl. Review, January, 1914.
Note: there are some scholars who think that the Letter to the Galatians predates the council. Concerning this question one can profitably consult Protestant scholar F.F. Bruce’s online article here. Fr. Raymond Brown suggests that it was written on the eve of the meeting in Jerusalem. Also, both Galatia and Corinth were outside the territories addressed: The city of Antioch, and the territories of Syria and Cilicia. In other words, the original injunction may have been applicable only to the people in these areas, not elsewhere.