For Moses said, ‘Honor your father and your mother’ (Exodus 20:12. Deuteronomy 5:16), and also, ‘Whoever speaks evil of his father or mother, let him be condemned to death’ (Exodus 21:16. Leviticus 20:9).
Christ now gives an example to show the real consequence of their deviation. He appeals to the Mosaic Law and recalls the commandment to honor parents (Exodus 20:12, Deut. 5:16), which was among the foundational moral commandments of the covenant. He also recalls its seriousness, showing that dishonor and slander against parents (Exodus 21:16, Lev. 20:9) are a grave sin in God’s sight and subject to strict judgment. Thus the Lord shows that this is not about a secondary regulation, but about the holiness of human relationships, established by God’s own Law. God willed that there be honor, care, and order in the family, which includes not only respect but also practical care and responsibility toward parents. When that commandment is broken, it is not only the well-being of the family that is undermined, but obedience to God’s authority is also harmed. By this example Christ prepares to show how, by their traditions, they were in practice nullifying this commandment.