The Greek expression is stronger and means betrayal or treason. They said he preached that they should not circumcise their children and should not walk according to the customs, that is, should not fulfill the rites of the law of Moses.
These are evidently the same opponents of Paul, the teachers who troubled the Church of Antioch and Jerusalem. They demanded circumcision and observance of the law of Moses even for Gentiles turning to Christ (ch. 15).
After the apostolic decree that Gentiles were free from this, they settled on another claim. Jews, they said, when passing into Christianity, could not and must not be free from circumcision.
They laid against Paul the charge that he was an apostate from the law and taught apostasy from Moses.
The accusation against Paul, spread among the people in this form, was manifest slander. From all his teaching, as it is unfolded in his epistles, and from all his activity, it is clear what he taught and defended.
He taught that the salvation of those who believe in Christ is not conditioned at all by circumcision or by fulfillment of the law of Moses. It is conditioned by faith in Christ Jesus.
He taught that by the law alone, together with circumcision, man cannot be justified before God. He is justified apart from the law by faith in Christ, and so forth. See Romans, Galatians, and Corinthians.
But that he disparaged the law as God-given, or taught apostasy from it, was not the case.
The main thing is faith in Christ. The law of Moses is not essential for a Christian. Keep it if you wish; this is good, but do not hope to receive salvation through it.
If you do not wish, do not keep it. You will not be deprived of salvation if you believe in Christ and live as a Christian.
The believing Gentiles were freed by the apostolic council from the yoke of the law of Moses, and they will be saved. Therefore a Jew who has believed in Christ can also be saved apart from circumcision and observance of the law of Moses.
The law is not decisive here. One may fail to be saved while observing it, and one may be saved without observing it. Therefore, if you wish, observe it; if you wish, do not.
This is the Apostle’s teaching concerning the law. How he taught about circumcision is witnessed by his action when he took Timothy as his fellow worker and circumcised him (Acts 16:1-3 and note).
Thus the insinuation that Paul was an apostate from the law and taught others apostasy was a malicious insinuation and slander against the great Apostle.