Paul and company left the brethren at Caesarea with their offering to the poor at Jerusalem (Acts 21:15) and went up to the brethren there. They were received by James and the elders, but it was told Paul that many of the elders had been told that he was teaching Jews everywhere that they need not obey Moses and circumcise their children. This was a different charge than he was laden with in Acts 15. There he was accused of deserting Moses by not compelling believing gentiles to become circumcised. Now he is accused of deserting Moses by telling observant Jews they need not circumcise their children.
The charge, of course, was untrue. Paul’s manner was to the Jew he became as a Jew in order to win him to Christ (1Corinthians 9:21). By this time in Acts Paul had written Galatians, 1 & 2 Thessalonians ,1 & 2 Corinthians and Romans and probably in that order. It can be shown that he taught that circumcision was not necessary for salvation (1Corinthians 7:19), but no more than this. But the apostles in Jerusalem taught this (Acts 4:10-12). Nevertheless, James urged Paul to go into the Temple with four men who had a vow and share in the charges with them, according to Numbers 6:13-20, in order that the argument of some, that Paul taught against obedience to the Law, would be rendered moot.
I have read that some scholars believe a split among the brethren was imminent among the Jews at Jerusalem over this issue. And, I think there may be some truth to this, although Paul may have been used as an excuse, because John tells us that some Jewish brethren did break away some time later (1John 2:19), and the same is implied by Jude, the brother of James and son of Alphaeus (Jude 1:19). Moreover, we must remember that Paul also taught that at least some of those of the party of the circumcision who had sought to undo his work among the gentiles were “false” brethren (Galatians 2:1-4). These were planted within the body of Jewish believers by the sect of the Pharisees and/or the sect of the Sadducees in order to spy out what the new Jewish sect was about and to perhaps bring the Messianic Jews more in line with what was taught among those who rejected Jesus as the Messiah.
In any event, Paul did as James asked, but, just as the Holy Spirit had predicted (Acts 20:22-23), Paul was seized by the Jews, believing he had brought gentiles into the Temple to pollute it, and drove him out of the Temple and would have killed him, had it not been for the Roman captain who rescued Paul from the intent of the multitude. Nevertheless, he was put in chains and held by the Romans, until satisfaction could be obtained over why an insurrection occurred over his presence in the Temple.