At the end of Deuteronomy, Moses sets life and death before Israel and calls them to choose life. The command, he says, is not too hard or out of reach: the word is very near, in their mouth and in their heart. Paul later quotes that exact sentence to describe the word of faith he preached.
Not a summary of these passages: the passages themselves. Read them, then come back to the study below.
The study
What the Scripture says
1
The promise reaches past the curse
Deuteronomy 30 begins with the worst case already in view: the blessing and the curse have come and the people are scattered among the nations. Even there, Moses says, if they return, God will gather them from the uttermost parts of the heavens and bring them back. And He goes further than return, promising to circumcise their hearts so that they can love Him, which is what the law alone could never produce.
It shall happen, when all these things have come on you, the blessing and the curse, which I have set before you, and you shall call them to mind among all the nations, where Yahweh your God has driven you, and return to Yahweh your God, and obey his voice according to all that I command you this day, you and your children, with all your heart, and with all your soul; that then Yahweh your God will release you from captivity, have compassion on you, and will return and gather you from all the peoples where Yahweh your God has scattered you. If your outcasts are in the uttermost parts of the heavens, from there Yahweh your God will gather you, and from there he will bring you back. Yahweh your God will bring you into the land which your fathers possessed, and you will possess it. He will do you good, and increase your numbers more than your fathers. Yahweh your God will circumcise your heart, and the heart of your seed, to love Yahweh your God with all your heart, and with all your soul, that you may live.And it shall come to pass, when all these things are come upon thee, the blessing and the curse, which I have set before thee, and thou shalt call them to mind among all the nations, whither the Lord thy God hath driven thee, And shalt return unto the Lord thy God, and shalt obey his voice according to all that I command thee this day, thou and thy children, with all thine heart, and with all thy soul; That then the Lord thy God will turn thy captivity, and have compassion upon thee, and will return and gather thee from all the nations, whither the Lord thy God hath scattered thee. If any of thine be driven out unto the outmost parts of heaven, from thence will the Lord thy God gather thee, and from thence will he fetch thee: And the Lord thy God will bring thee into the land which thy fathers possessed, and thou shalt possess it; and he will do thee good, and multiply thee above thy fathers. And the Lord thy God will circumcise thine heart, and the heart of thy seed, to love the Lord thy God with all thine heart, and with all thy soul, that thou mayest live.
Moses answers the excuse before anyone makes it. The commandment is not too hard or too distant: it is not in heaven, that someone must go up and bring it down, and it is not beyond the sea, that someone must cross and fetch it. 'But the word is very near to you, in your mouth and in your heart, that you may do it.' God's demand never needed a heroic journey; it needed a heart.
For this commandment which I command you this day is not too hard for you or too distant. It is not in heaven, that you should say, “Who will go up for us to heaven, and bring it to us, and proclaim it to us, that we may do it?” Neither is it beyond the sea, that you should say, “Who will go over the sea for us, and bring it to us, and proclaim it to us, that we may do it?” But the word is very near to you, in your mouth and in your heart, that you may do it.For this commandment which I command thee this day, it is not hidden from thee, neither is it far off. It is not in heaven, that thou shouldest say, Who shall go up for us to heaven, and bring it unto us, that we may hear it, and do it? Neither is it beyond the sea, that thou shouldest say, Who shall go over the sea for us, and bring it unto us, that we may hear it, and do it? But the word is very nigh unto thee, in thy mouth, and in thy heart, that thou mayest do it.
Romans 10 quotes Moses' words and turns them toward Christ: do not ask who will ascend into heaven, that is, to bring Christ down, or who will descend into the abyss, that is, to bring Him up from the dead. What does it say? The word is near you, in your mouth and in your heart, that is, the word of faith we preach. Then Paul names the content of that faith: confess with your mouth that Jesus is Lord, and believe in your heart that God raised Him from the dead.
For Moses writes about the righteousness of the law, “The one who does them will live by them.” But the righteousness which is of faith says this, “Don’t say in your heart, ‘Who will ascend into heaven?’ (that is, to bring Christ down); or, ‘Who will descend into the abyss?’ (that is, to bring Christ up from the dead.)” But what does it say? “The word is near you, in your mouth, and in your heart”; that is, the word of faith, which we preach: that if you will confess with your mouth that Jesus is Lord, and believe in your heart that God raised him from the dead, you will be saved. For with the heart, one believes unto righteousness; and with the mouth confession is made unto salvation. For the Scripture says, “Whoever believes in him will not be disappointed.” For there is no distinction between Jew and Greek; for the same Lord is Lord of all, and is rich to all who call on him. For, “Whoever will call on the name of the Lord will be saved.”For Moses describeth the righteousness which is of the law, That the man which doeth those things shall live by them. But the righteousness which is of faith speaketh on this wise, Say not in thine heart, Who shall ascend into heaven? (that is, to bring Christ down from above:) Or, Who shall descend into the deep? (that is, to bring up Christ again from the dead.) But what saith it? The word is nigh thee, even in thy mouth, and in thy heart: that is, the word of faith, which we preach; That if thou shalt confess with thy mouth the Lord Jesus, and shalt believe in thine heart that God hath raised him from the dead, thou shalt be saved. For with the heart man believeth unto righteousness; and with the mouth confession is made unto salvation. For the scripture saith, Whosoever believeth on him shall not be ashamed. For there is no difference between the Jew and the Greek: for the same Lord over all is rich unto all that call upon him. For whosoever shall call upon the name of the Lord shall be saved.
Moses calls heaven and earth as witnesses and sets the two paths plainly: life and prosperity, or death and evil. His summary of the good path is not rule-keeping for its own sake but love, obedience, and clinging, 'for he is your life, and the length of your days.' And the command is 'Therefore choose life, that you may live', which is still the shape of the gospel invitation.
Behold, I have set before you this day life and prosperity, and death and evil. For I command you this day to love Yahweh your God, to walk in his ways, and to keep his commandments, his statutes, and his ordinances, that you may live and multiply, and that Yahweh your God may bless you in the land where you go in to possess it. But if your heart turns away, and you will not hear, but are drawn away, and worship other gods, and serve them; I denounce to you this day, that you will surely perish. You will not prolong your days in the land where you pass over the Jordan to go in to possess it. I call heaven and earth to witness against you this day, that I have set before you life and death, the blessing and the curse. Therefore choose life, that you may live, you and your descendants; to love Yahweh your God, to obey his voice, and to cling to him; for he is your life, and the length of your days; that you may dwell in the land which Yahweh swore to your fathers, to Abraham, to Isaac, and to Jacob, to give them.See, I have set before thee this day life and good, and death and evil; In that I command thee this day to love the Lord thy God, to walk in his ways, and to keep his commandments and his statutes and his judgments, that thou mayest live and multiply: and the Lord thy God shall bless thee in the land whither thou goest to possess it. But if thine heart turn away, so that thou wilt not hear, but shalt be drawn away, and worship other gods, and serve them; I denounce unto you this day, that ye shall surely perish, and that ye shall not prolong your days upon the land, whither thou passest over Jordan to go to possess it. I call heaven and earth to record this day against you, that I have set before you life and death, blessing and cursing: therefore choose life, that both thou and thy seed may live: That thou mayest love the Lord thy God, and that thou mayest obey his voice, and that thou mayest cleave unto him: for he is thy life, and the length of thy days: that thou mayest dwell in the land which the Lord sware unto thy fathers, to Abraham, to Isaac, and to Jacob, to give them.
Yahweh your God will circumcise your heart, and the heart of your seed, to love Yahweh your God with all your heart, and with all your soul, that you may live.And the Lord thy God will circumcise thine heart, and the heart of thy seed, to love the Lord thy God with all thine heart, and with all thy soul, that thou mayest live.
But the word is very near to you, in your mouth and in your heart, that you may do it.But the word is very nigh unto thee, in thy mouth, and in thy heart, that thou mayest do it.
I call heaven and earth to witness against you this day, that I have set before you life and death, the blessing and the curse. Therefore choose life, that you may live, you and your descendants;I call heaven and earth to record this day against you, that I have set before you life and death, blessing and cursing: therefore choose life, that both thou and thy seed may live:
that if you will confess with your mouth that Jesus is Lord, and believe in your heart that God raised him from the dead, you will be saved.That if thou shalt confess with thy mouth the Lord Jesus, and shalt believe in thine heart that God hath raised him from the dead, thou shalt be saved.