Heresy
Pope St. Gregory stigmatized Judaism and the Jewish People in many of his writings. He described Jews as enemies of Christ: "The more the Holy Spirit fills the world, the more perverse hatred dominates the souls of the Jews." He labeled all heresy as "Jewish", claiming that Judaism would "pollute [Catholics and] deceive them with sacrilegious seduction." The identification of Jews and heretics in particular occurred several times in Roman-Christian law,

Q: In what culture of law were Jews and heretics often lumped together?
Roman-Christian law