Roman Catechism 19.146

Chapter 19 — Part II: The Sacraments — Penance

Section 146. In Exodus, too, we read that though the Lord yielded to the prayers of Moses and spared the idolatrous Israelites, yet He threatened the enormity of their crime with heavy chastisement, and Moses himself declared that the Lord would take severest vengeance on it, even to the third and fourth generations.