The Faithfulness of God
"What if some were unfaithful? Does their faithlessness nullify the faithfulness of God? By no means! Let God be true though every one were a liar, as it is written, 'That you may be justified in your words, and prevail when you are judged.'"
At the beginning of Romans 3, Paul takes a brief break from his argument that Jews and Gentiles are both equally under the condemnation of the Lord because of their sin. His aim in this passage is to make sure that his readers do not misunderstand what he has been saying about the Jewish people. He explains that the Jews will not escape judgment merely because they are Jews. This is because, if one wants to rest in the Jewish privileges of the law and circumcision for justification, one must be keep the commandments perfectly (Rom. 2). There are, nevertheless, many benefits that Jews possess. Chief among these are the "oracles of God"—the living and active Word of God, namely, the Hebrew Scriptures or Old Testament (3:1–2).
The Apostle moves from the notion of the Lord entrusting the Jews with His Word— His putting "faith" in them to keep His commandments—and in today's passage focuses on the antithesis of God's trust, which is the Jews' faithlessness. He is seeking to answer the question as to whether God will continue to be faithful to His covenant even though the people to whom He has bound Himself in covenant relationship have rejected this bond by their sin (v. 3). Even to ask this question is to answer it, as is seen in Paul's reply "By no means!" or as some other translations put it, "God forbid!" (v. 4). Since the Lord has shown Himself faithful time and again (Deut. 7:9; Ps. 71:22), the suggestion that God might not uphold His end of the covenant is ridiculous. Our holy Creator is always true even though all men are liars and in various ways compromise the truth and break the covenant (Rom. 3:4).
However, this raises the issue as to what God's faithfulness actually means in relation to His covenant. God promised great blessing to the Israelites (Gen. 12:1–3), and so under the old covenant, the Jews rightly equated divine faithfulness with His blessing upon them. The problem, however, was that too many of them ignored the double-edged sword of the Lord's promises. For it is likewise true that God promised Abraham that He would curse those who did not keep His covenant (17:1–14), which ultimately means judgment on those who are uncircumcised in heart (Rom. 2:25–29). The only way God can be faithful to His covenant is to judge sinners, so the condemnation that Paul is pronouncing on Jewish sinners is not evidence of the Lord's unfaithfulness. Instead, it is proof that He always keeps His Word. To be faithful to His covenant, God must judge sin.
Coram Deo
The notion that the Lord must judge sin in order to be faithful is developed in more detail at the end of Romans 3. Paul cites Psalm 51 in today’s passage because in this prayer of confession, David points out that God shows His faithfulness by turning against sin. In Christ, we are rescued from this judgment, but understanding the gospel starts with knowing that our holy God cannot be faithful to His Word without finding a way to judge our sin. Proclaiming His wrath is part of the gospel.