In a famous passage of the Sermon on the Mount (Matt 5:17–20) Jesus proclaims that he has not come to abolish the law but to fulfil it. The Gospel of Matthew was probably written for a Jewish audience, and its author presumed that Jews continue to obey the legal obligations of the Torah. The passage seems to claim that legal observance is necessary for salvation, which disturbed many of its later Christian readers. The article analyzes how the saying influenced both Western and Eastern Christian legal thought in late antiquity. Through the satirical Talmudic story (Bavli, Shabbat 116ab), which refers specifically to Matthew, the article also shows how rabbinic legal understanding modifies Christian traditions of the passage.