"Probably the best description of Judaizers is in Acts 15:1: "And certain men came down from Judea and taught the brethren, and said, 'Unless you are circumcised according to the custom of Moses, you cannot be saved.'
This behavior was particularly persecuted from 1300 to 1800 during the Spanish and Portuguese Inquisitions, using as a basis the many references in the Pauline epistles regarding the "Law as a curse" and the futility of relying on the Law for attaining salvation, known as legalism.