who keeps faithfulness for thousands, who forgives wrongdoing, violation of His Law, and sin; yet He will by no means leave the guilty unpunished, inflicting the punishment of fathers on the children and on the grandchildren to the third and fourth generations.” Exodus 34:7 NASB
Yet by no means leave – This is a bit tricky, so pay attention. Here is the Hebrew text:
נֹצֵ֥ר חֶ֨סֶד֙ לָֽאֲלָפִ֔ים נֹשֵׂ֥א עָוֹ֛ן וָפֶ֖שַׁע וְחַטָּאָ֑ה וְנַקֵּה֙ לֹ֣א יְנַקֶּ֔ה פֹּקֵ֣ד | עֲוֹ֣ן אָב֗וֹת עַל־בָּנִים֙ וְעַל־בְּנֵ֣י בָנִ֔ים עַל־שִׁלֵּשִׁ֖ים וְעַל־רִבֵּעִֽים
I’ve highlighted the critical words in red. Now the transliteration (in case you don’t read Hebrew) of the highlighted words:
venake lo yenake.
As you can plainly see, the root is the same in both words. The English translation disguises this fact, but it wasn’t hidden from the rabbis. The root is nāqâ, “The root nāqâ with the meaning ‘to be clean, pure, spotless’ is found in Akkadian, Arabic and Aramaic. In Dan 7:9 [Aramaic] the Ancient of Days is described as having hair ‘like pure (nĕqēʾ) wool.’ The derived juridical notion ‘to be acquitted,’ ‘to go unpunished’ is found only in Hebrew.”
Notice what Akiva discovers in this double use of the root:
“If Rabbi Akiva was strict regarding mitzvot between human and God, he was even more so in the case of mitzvot between human beings and human beings. The verse says, “yet not clearing, clearing the guilty’ (Exodus 34:7). Rabbi Akiva expounded: ‘One phrase says ‘clearing (nakkeh)’ and one phrase says ‘not clearing (lo yenakkeh).’ How can this contradiction be reconciled? ‘Clearing’ refers to the mitzvot between human beings and God. ‘Not clearing’ refers to the mitzvot between human beings and human beings.”
Akiva’s insight provides us with a description of two actions in the process of punishment. The first deals with our offenses before God. Exodus 34:7 tells us that God will deal with these. But there is also another kind of sin that needs to be punished, the sins we perpetuate on other human beings. God tells us that He will also deal with these. We do not escape judgment simply by begging forgiveness from God. “Against You only I have sinned,” is not sufficient. God reminds us that we must also account for our sins against others. Reconciliation, if possible, means dealing with both God and men. Clearing and not clearing.
Topical Index: nāqâ, clear, acquit, punish, Akiva, Exodus 34:7
 Abraham Heschel, Heavenly Torah as Refracted through the Generations, p. 177.