Acts 21
20 And when they heard it, they glorified the Lord. And they said to him, “You see, brother, how many myriads of Jews there are who have believed, and they are all zealous for the law; 21 but they have been informed about you that you teach all the Jews who are among the Gentiles to forsake Moses, saying that they ought not to circumcise their children nor to walk according to the customs. 22 [d]What then? The assembly must certainly meet, for they will hear that you have come. 23 Therefore do what we tell you: We have four men who have taken a vow. 24 Take them and be purified with them, and pay their expenses so that they may shave their heads, and that all may know that those things of which they were informed concerning you are nothing, but that you yourself also walk orderly and keep the law. 25 But concerning the Gentiles who believe, we have written and decided [e]that they should observe no such thing, except that they should keep themselves from things offered to idols, from blood, from things strangled, and from [f]sexual immorality.”

A couple of things stand out here.
There are people ministering in Jerusalem currently, and Paul met with them. Based on the information they gave Paul in this scripture, the law and the customs are more important than truth to the local Jews.

The Jews Paul met with explained he should shave his head a walk according to the law so that the local Jews do not believe the information they have heard about Paul.

They also explained that there are different rules for Jews and Gentiles.

It seems like the “brethren” Paul is meeting with have conformed to local ideas so that they blend in and do not cause any commotion. This is terrible. They should be standing out and walking in victory, not becoming like the rest.