As you read chapter twenty-one, you will see numerous echoes of Jesus’ life. It would be going too far to equate Paul with Jesus, but it is within the purpose of the book to show that Jesus’ disciples followed in Jesus’ footsteps.
Thus we see Paul anxious to go to Jerusalem (compare Luke 9:51 with Acts 20:16), just as Jesus was. Paul is determined to go there despite the fact that prison and hardships await him (compare Luke 13:33 with Acts 20:23), just as Jesus knew that death awaited him there. The hardships awaiting them were both according to the will of God (Luke 24:45ff and Acts 21:14). Paul’s experience in the temple mirrors that of Jesus: he is falsely accused and convicted by rumor. Through it all, the reader understands that like Jesus, Paul was innocent.
Chapter twenty-one illustrates well the tight-rope leadership sometimes has to walk. Paul arrived with a large contribution for the relief of the Jerusalem church. Neither Luke nor the leadership of the church mention it. Something more momentous is afoot. The rumor is the Paul tells Jews they don’t have to obey the law nor adhere to Jewish customs. This was untrue, of course. Paul had even taken a vow according to Jewish law (Acts 18:18). What Paul had taught was that keeping Jewish customs did not merit the blessing of God. But folks tend to believe what they want to believe regardless of the facts.
The Elders ask Paul to undergo purification rites (he had, after all, been in gentile territory) and pay for the vows of four men. The cost was considerable and Paul is being asked to foot the bill. The whole purpose was to scotch the chance of trouble in the church. Paul, to his credit, realized that such needed to be done for the sake of unity. Unfortunately, things went down hill from there.
Did the Elders and Paul do right? Absolutely. Paul could have asserted his freedom not to do it, but Paul was not in bondage to his freedom. He had written just a few years before: “19 Though I am free and belong to no one, I have made myself a slave to everyone, to win as many as possible” (1 Corinthians 9:19). Sometimes we have to take a step back as individuals so we can go forward together as the people of God.