The Jewish believers experienced a gradual revelation of the impotence of the temple sacrifices and priesthood and the all-sufficiency of the heavenly temple, high priest and once all-sufficient sacrifice of the cross. The book of Hebrews was specifically addressed to the Jewish Church to enlighten them on this matter and assist them in turning their back on the removed Old Testament practices. The destruction of the temple removed the last vestige of old covenant thinking that had attached itself to the Jewish Church. They were now finally separated from the old.
Albert Barnes contends, speaking about the Christian leaders in Jerusalem instructing Paul to submit to the Jewish customs in order to gain credibility: “It is evident that James and the elders meant to say that these men were connected with them in the Christian church; and the fact shows that the Christians at Jerusalem did not disregard the institutions of Moses, and had not been so far enlightened in the doctrines of Christianity as to forsake yet the ceremonial rites of the Jews.”
Asked 21:15–25: “And the day following Paul went in with us unto James; and all the elders were present. And when he had saluted them, he declared particularly what things God had wrought among the Gentiles by his ministry. And when they heard it, they glorified the Lord, and said unto him, Thou seest, brother, how many thousands of Jews there are which believe; and they are all zealous of the law: And they are informed of thee, that thou teachest all the Jews which are among the Gentiles to forsake Moses, saying that they ought not to circumcise their children, neither to walk after the customs. What is it therefore? the multitude must needs come together: for they will hear that thou art come. Do therefore this that we say to thee: We have four men which have a vow on them; Them take, and purify thyself with them, and be at charges with them, that they may shave their heads: and all may know that those things, whereof they were informed concerning thee, are nothing; but that thou thyself also walkest orderly, and keepest the law. As touching the Gentiles which believe, we have written and concluded that they observe no such thing, save only that they keep themselves from things offered to idols, and from blood, and from strangled, and from fornication.”
The Jewish leader leaders forced Paul to go to the temple to prove his Jewish credentials. This was not voluntary. He did it under duress. It clearly was a sop to the Christ-rejecting Jews.