The objector tries the argument again in personal terms. If my lie makes God's truth shine brighter and brings Him glory, why am I still judged as a sinner? Barnes explains that "the truth of God" here means "His truth or faithfulness in adhering to his threatenings." The objector's mistake, Barnes says, is to assume that "the direct tendency of his conduct is to promote God's glory." Gill notes that God's truth is "commended, illustrated, and made to abound" by contrast with human lies, yet "their sins are nevertheless sins."

Paul answers with a question of his own that shows where this thinking leads: "And not rather ... Let us do evil, that good may come?" (Romans 3:8). Some were already slandering Paul by claiming he taught exactly that. His verdict on such reasoning is short: "whose damnation is just" (Romans 3:8).

Paul argues here by voicing an opponent's objection and then answering it, a style he uses throughout Romans (Romans 3:1, 5, 7; 9:19). The "I" in this verse is not Paul confessing his own lie. Gill says the apostle speaks "in the person of a sinful man."

The "lie" sets up the contrast with Romans 3:4: "let God be true, but every man a liar." Paul had just quoted Psalm 51:4, where David owned that God was right to judge his sin.

This is an excuse dressed up as theology. The objector does not deny his lie; he tries to credit it to God's glory. But God is glorified by His own truth, not by our falsehood. Barnes says sin works the opposite way from what the objector claims.

Paul's answer protects both God's honor and the seriousness of sin. The same chapter goes on to show that "all have sinned" and that sinners are "justified freely by his grace" (Romans 3:23-24). The answer to sin is not to excuse it but to receive God's grace.