But the righteousness that is by faith says: "Do not say in your heart, 'Who will ascend into heaven?'" (that is, to bring Christ down) "or 'Who will descend into the deep?'" (that is, to bring Christ up from the dead) (vv. 6-7).

This passage is often misunderstood, yet the overall meaning of it is somewhat easy to understand and well-quoted in the church. If your mind is caught up too much with the phrase, "Do not say" in a legalistic sense, then, you will miss the point. Keep in mind that the opposite of faith is unbelief. To say, "Who will ascend into the deep?" or "Who will descend into the deep?" is an indication of unbelief. Therefore, "the righteousness that is by faith" does not say and ask those questions. Also, do not be misled by the expressions, "to bring Christ down," and "to bring Christ up from the dead," into thinking that these things are something that believers should not do, again, in a legalistic sense. No, as the phrase, "that is," indicates, Paul is explaining how each sentence he quotes should be understood. It should be realized that he interprets this section of Deuteronomy 30 in terms of a prophecy and its fulfillment concerning Christ who descended from heaven to the earth, and then, ascended from hell to bring the word near to humans so that they can do what it says. For him, "that is" means "it is to be understood as …," or even "it came to be fulfilled as …" In other words, God did exactly the impossible things that people say were the reason for not being able to obey God's commandments, so that they could obey them.

But what does it say? "The word is near you; it is in your mouth and in your heart," that is, the word of faith we are proclaiming (v. 8).

He quotes from Deut 30:14 as a conclusion, and says that it came to be fulfilled in Christ whose gospel he is preaching. Since the emphasis is on "believing" in this particular portion of the letter, he leaves out the last part of that verse in Deuteronomy so that it does not cause misunderstanding.

No, the word is very near you; it is in your mouth and in your heart so you may obey it (Deut 30:14).

God's ultimate purpose of sending Christ was to make those who were saved by faith would do the will of God obeying his law.

It seems that behind this way of interpreting the above passage in Deuteronomy, there was an interesting belief among the Christians in the early church concerning how Christ descended to hell and what he did there.

… (spirit), through whom (in which) also he went and preached to the spirits in prison who disobeyed long ago when God waited patiently in the days of Noah while the ark was being built (1 Pet 3:19-20).

Needless to say, the purpose of Christ's preaching to these spirits was not to save them, but to proclaim victory over them. These spirits represent the force that causes people to sin in this world, and Christ demonstrated, before them, the authority and the power that had been taken away from humans because of their sins, but was regained through his death, and they all saw him ascending from hell as the disciples saw him ascending from the earth. This was done so that they could no longer bother those who would come to believe in him. We believers are finally able to do the will of God freely by being led by the Spirit of God. And on the way back from hell, Christ placed a stone at the exit—the spot on the floor of the Most Holy Place in the temple, where the Ark was once placed. This is the stone in Isaiah 28:16—"a stone in Zion, a tested (approved) stone," traditionally called "shetiyyah." Note how the passage in Isaiah 28 depicts those who think that they will not descend into the deep because they made an agreement with the grave (she'ol), but in fact, will all fall into it through this entrance. At the same entrance, this stone was placed so that "the one who trusts (believes) will never dismayed."