(Rom 3:1-4 NET) Therefore what advantage does the Jew have, or what is the value of circumcision? 2 Actually, there are many advantages. First of all, the Jews were entrusted with the oracles of God. 3 What then? If some [of the Jews] did not believe, does their unbelief nullify the faithfulness of God? 4 Absolutely not! Let God be proven true, and every human being shown up as a liar, just as it is written: “so that you will be justified in your words and will prevail when you are judged.”
Why might the unbelief of the Jews nullify God’s faithfulness? Faithfulness to what? Well, plainly, to God’s covenants with the Jews.
Many Christian readers miss this because they haven’t read the many parallel OT texts, such as —
(Exo 2:23-24 ESV) During those many days the king of Egypt died, and the people of Israel groaned because of their slavery and cried out for help. Their cry for rescue from slavery came up to God. 24 And God heard their groaning, and God remembered his covenant with Abraham, with Isaac, and with Jacob.
(Psa 89:30-34 ESV) 30 If his children forsake my law and do not walk according to my rules, 31 if they violate my statutes and do not keep my commandments, 32 then I will punish their transgression with the rod and their iniquity with stripes, 33 but I will not remove from him my steadfast love or be false to my faithfulness. 34 I will not violate my covenant or alter the word that went forth from my lips.
(Isa 54:10 ESV) 10 For the mountains may depart and the hills be removed, but my steadfast love shall not depart from you, and my covenant of peace shall not be removed,” says the LORD, who has compassion on you.
One of the recurring OT themes is God’s faithfulness to his covenants. Repeatedly this is the stated motivation for God’s actions.
It’s no surprise that Paul speaks of God’s faithfulness — assuming that we’ll understand that he is, of course, speaking of faithfulness to his covenants with Abraham, Israel, and David.
This brings us to —
(Rom 3:5-7 NET) 5 But if our unrighteousness demonstrates the righteousness of God, what shall we say? The God who inflicts wrath is not unrighteous, is he? (I am speaking in human terms.) 6 Absolutely not! For otherwise how could God judge the world? 7 For if by my lie the truth of God enhances his glory, why am I still actually being judged as a sinner?
Now, recall that God established his covenant with Abraham so that he and his descendants would be just and righteous —
(Gen 18:19 ESV) “For I have chosen him, that he may command his children and his household after him to keep the way of the LORD by doing righteousness and justice, so that the LORD may bring to Abraham what he has promised him.”
Hence, in Rom 3:5, “our unrighteousness” is our sin, of course, but more exactly our unfaithfulness to the covenants.
When God responds to our unrighteousness with punishment, God is not being “unrighteous,” that is, he is not violating the covenant he made. God’s “righteousness” is another way of referring to his covenant faithfulness. (And this sets the stage for the interpretation of the rest of the chapter.) After all, God very clearly specifies in Lev 26 and Deu 27-29 that there will be severe punishment for Israel if Israel violates the covenant. God will be patient and give Israel time to repent, but ultimately, God will be honoring his covenant by invoking punishment — that is, his wrath.
(Deu 29:27-28 ESV) 27 Therefore the anger of the LORD was kindled against this land, bringing upon it all the curses written in this book, 28 and the LORD uprooted them from their land in anger and fury and great wrath, and cast them into another land, as they are this day.
So God is faithful, even when our faithlessness invokes his wrath. But God has promised to restore his people from Exile if they’ll return to him. He promised to circumcise their hearts himself so that they will obey him and live (Deu 30:6). This is also part of God’s covenant faithfulness.