Roman Catechism 24.48

Chapter 24 — Part III: The Decalogue — The First Commandment

Section 48. "Visiting The Iniquity," Etc. — Concerning the threat contained in this Commandment it should be explained that God will not suffer sinners to go unpunished, but will chastise them as a father, or punish them with the rigour and severity of a judge. This was elsewhere explained by Moses when he said: Thou shalt know that the Lord thy God is a strong and faithful God, keeping his covenant and mercy to them that love him, and to them that keep his commandments, unto a thousand generations; and repaying forthwith them that hate him. You will not, says Josue, be able to serve the Lord; for he is a holy God, and mighty and jealous, and will not forgive your wickedness and sins. If you leave the Lord and serve strange gods, he will turn and will afflict you, and will destroy you.