As familiar as this verse is, parts of it are obscure and even appear contradictory. In his Aramaic translation, Onkelos clarifies it with insertions to fill in the gaps. He renders this verse: "(G-d) extends mercy to the thousandth generation, forgiving iniquity and transgression and sin. He cleanses those who return to His Torah; He will not not cleanse those who do not return, visiting the sin of the fathers on the children and on the children's children who rebel to the third generation and the fourth generation."