Now, there’s more to it. Paul begins the discussion with –
(Rom 10:5-8 ESV) For Moses writes about the righteousness that is based on the law, that the person who does the commandments shall live by them. 6 But the righteousness based on faith says, “Do not say in your heart, ‘Who will ascend into heaven?'” (that is, to bring Christ down) 7 “or ‘Who will descend into the abyss?'” (that is, to bring Christ up from the dead). 8 But what does it say? “The word is near you, in your mouth and in your heart” (that is, the word of faith that we proclaim);
He is writing midrash on Deu 30 —
(Deu 30:11-14 LXX) For this command which I give thee this day is not grievous, neither is it far from thee. 12 It is not in heaven above, as if there were one saying, Who shall go up for us into heaven, and shall take it for us, and we will hear and do it? 13 Neither is it beyond the sea, saying, Who will go over for us to the other side of the sea, and take it for us, and make it audible to us, and we will do it? 14 The word is very near thee, in thy mouth, and in thine heart, and in thine hands to do it.
Back in Deu 27-29, God threatened exile and a long list of curses should Israel violate its covenant with God. This came to pass with the Babylonian Captivity — and to most Jews of Paul’s day, was considered to be still ongoing.
Yes, the Persians had allowed Ezra and Nehemiah to bring some Jews back to Jerusalem to rebuild the temple and the city, but the vast majority of Jews remained dispersed throughout the Empire (the Diaspora), and the promises God made regarding the end of the Exile had not yet come true. The end of the Exile was to bring the Kingdom, the Messiah, and the outpoured Spirit — among many other things.
In Deu 30, Moses is promising an end to the Exile, especially —
(Deu 30:6 ESV) 6 And the LORD your God will circumcise your heart and the heart of your offspring, so that you will love the LORD your God with all your heart and with all your soul, that you may live.
In parallel with Jer 31:31 ff and Heb 8, God promises that, when the Kingdom comes, God himself will change the hearts of his people so that they will become obedient — and love God with all their heart and soul — and so live.
In Deu 30:11-14, Moses is saying that returning to God so that this will happen is not that hard. It’s well within the Jews’ ability to come back to God. It’s not as though you have to ascend to heaven or cross the seas to find out how to return to God!
Paul explains this passage in Rom 10:5-8 to say that you don’t have to drag Jesus down from heaven or pull him up out of the grave. Obviously, God has already done this for you. Jesus himself may not be physically present, but his word (message, the gospel) is already available to confess.
In fact, it’s because of this passage (“The word is very near thee, in thy mouth, and in thine heart, and in thine hands to do it.”) that Paul so emphasizes confession (“in thy mouth”) and faith as being in our hearts (“in thine heart”). It’s not hard. It wasn’t meant to be hard. In fact, Moses promised it would easy.
In short — and I know I’m not doing this the easy way — Paul is saying that the end of Exile promised in Deu 30 will come to Israel just as soon as Israel believes in Jesus and confesses him — and it’s not that hard. But (and this is the point of the passage), for some reason, the Jews, on the whole, are rejecting Jesus.
For us today, of course, the relevance is both the necessity of faith in Jesus as well as the sufficiency of faith in Jesus — which is not supposed to be hard.
But what does it say? “The word is near you, in your mouth and in your heart” (that is, the word of faith that we proclaim)
That is, it’s already all present in the OT. Just be true to the scriptures (by believing in Jesus), and you’ll be saved!