Romans 10:5–8—Christ is not far away; he’s as close as your mouth and heart.

Faith in Christ is the single requisite for attaining eternal life. The problem for the Jews is that they persist in wanting to “do” the works of the law rather than “say” the confession of faith in Christ. In these verses Paul finds support for the principle of faith in the Jews’ own Scriptures. First, he highlights the risk of depending on one’s obedience. Then he takes away any excuse that the gospel is out of reach for anyone.

An implicit warning about relying on effort (verse 5)
Paul knows that some Jews, who seem to have a high opinion of their willpower and grit, think they can perfectly obey the law. So in verse 5 he confronts that mindset with part of a verse from Leviticus 18:5: “You shall therefore keep my statutes and my rules; if a person does them, he shall live by them: I am the LORD.”

Moses says that Israel’s enjoyment of life’s blessings is contingent on doing the commandments. The verse conceives of both blessing and penalty taking place in this life. Those who obey will enjoy the land; those who don’t obey it will be cut off from the people. But Paul makes his own application of the verse. Apparently he interprets “shall live” to mean “shall have eternal life.”

Paul realizes it’s hypothetically possible that a person who perfectly obeys the law could attain eternal life, but he also knows this is impossible because of sin. Who can say, for example, that they have been perfect in sexual conduct? The particular laws after this verse in Leviticus 18 deal with that very subject.

The commandment promises life but proves to be death, Paul said in 7:10. That’s the horrible consequence of righteousness based on the law. Next Paul will contrast it with the righteousness based on faith. The law properly understood, Paul seems to say, contains within it the principle of faith that points to Christ. It is in this sense, as opposed to self-righteously doing the works of the law, that the law can lead to eternal life.

Paul’s artful exegesis (verses 6–8)
These quotations are from Deuteronomy. Until we understand Paul’s meaning, his use of them may seem clumsy and arbitrary. Especially confusing is his use of a style of exegesis common in his day that allows him to convert these Scriptures to his own purpose. And to tip readers that he is altering their original meaning, three times he uses “that is” to signal he is reinterpreting and applying them to his gospel message about Christ.

Also, again in this epistle Paul uses the rhetorical device of personification. Righteousness based on faith “says” a message of heartfelt faith in contrast with what Moses “writes” in verse 5. Now let’s probe the Deuteronomy context to see how Paul gets to his point.

Grace and faith in Deuteronomy
Paul finds in Deuteronomy 30:11–14 a meaningful reference to faith that he applies to the gospel. Although the wording is difficult for us to comprehend, the believers in Rome would have understood. To them, the phrase “ascend into heaven” was akin to a proverb that meant vain effort to do an impossible task.

In effect, Moses tells the people not to think that it is out of reach for them to obey the commands of God’s covenant with them. Paul’s interest lies in the reason Moses gives: The commandment is near them because it resides in their mouth and heart:

The people in Moses’ day could act on God’s word because they could pronounce it with their mouth and ponder it in their heart. Likewise with the gospel in Paul’s day and ours—we can confess it with our mouth and receive it in our heart.

Another thing we don’t readily see, but the Roman believers most likely did see, is that Paul adds to the effectiveness of the quotation by taking the opening phrase “Do not say in your heart” from another Deuteronomy passage, 9:4. There Moses tells the people that God will go before them and drive out their enemies as they enter the land. Here is more of the verse: “Do not say in your heart, after the LORD your God has thrust them out before you, ‘It is because of my righteousness that the LORD has brought me in to possess this land’.”

This Deuteronomy 9 background reinforces the point Paul derives from chapter 30. The OT folks could obey the commandment and would prosper when they did so, but only when they relied on God’s grace, not their own righteousness. This is the context, then, that leads Paul to adapt this passage for proclamation of the new covenant gospel (as he will elaborate in verses 9 and 10).

Paul’s application to Christ
God’s word to his people in the OT was the law. Because Jesus is the end of the law (verse 4), Paul thought it reasonable to substitute Christ for the commandment of Deuteronomy 30. We don’t have to go to heaven to bring Christ down. He came down of his own initiative to take on human flesh and give up his life for our sins. And we don’t have to go down to the region of the dead to bring Christ up. (Paul replaced “sea” with “abyss,” denoting Sheol, the place of the dead.) He ascended in triumph by the power of God.

Douglas Moo further explains Paul’s reasoning: “As God brought his word near to Israel so they might know and obey him, so God now brings his word ‘near’ to both Jews and Gentiles that they might know him through his Son Jesus Christ and respond in faith and obedience.” And “just as Israel could not plead the excuse that she did not know God’s will, so now, Paul says, neither Jew nor Gentile can plead ignorance of God’s revelation in Jesus Christ.”

Christ did what was impossible for us so that we might do what is both possible and necessary: respond in faith to him. R. C. Sproul comments, “It is possible to have faith in the mouth and have no faith in the heart. But you cannot find faith in the heart that is not also in the mouth.”