“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:”
King James Version (KJV)
21:20 They are all zealous for the law - For the whole Mosaic dispensation. How astonishing is this! Did none of the apostles, beside St. Paul, know that this dispensation was now abolished? And if they did both know and testify this, how came their hearers not to believe them?
Ac 21:20-22 When they heard [it]. Paul's report of the wonderful success of the gospel. They evidently approved of and sympathized with his work. Thou seest, brother, now many thousands . . . believe. The Greek reads: "How many tens thousands". There were not only many thousands of Christians in the Jerusalem church, but many thousands of Jewish Christians who had come up to the feast of Pentecost. Twenty-seven years before there were five thousand men who believed in Jerusalem (Ac 4:4). They are all zealous for the law. "Zealots" for the law in the Greek. They believed upon Christ as the Messiah, but did not understand that the Old Covenant had passed away to give place to the New (Heb 8:13). Hence, while they observed the Christian rites, they still kept up the forms of Judaism. It took a direct interposition of the Spirit to teach that Gentiles were entitled to baptism without circumcision (Ac 10:46-48). It required a council in Jerusalem to settle the question that Gentile Christians were not to keep the Jewish law (Ac 15:19-21). God taught the church, lesson by lesson, but up to this time that at Jerusalem had not yet learned that they were freed from the obligation to keep the law of Moses.