For the promise that he would be the heir of the world was not to Abraham or to his seed through the law, but through the righteousness of faith. (Romans 4:13)
We often think of Abraham as one through whom the inheritance came. But Paul called him the heir of the world. An heir is one who receives an inheritance. Here we see that the inheritance Abraham was given is the world itself. When God called Abraham to leave his father's house and his country, He gave him this promise:
I will make you a great nation;The blessing for all the families of the earth comes through Abraham. He is the father of numberless descendants, the father of multitudes, the father of nations and kings. This is the inheritance Abraham received from God, and it is the inheritance he passes on to all those who are heir to him.
I will bless you
And make your name great;
And you shall be a blessing.
I will bless those who bless you,
And I will curse him who curses you;
And in you all the families of the earth shall be blessed.
Then He brought him outside and said, “Look now toward heaven, and count the stars if you are able to number them.” And He said to him, “So shall your descendants be.” (Genesis 15:5)
Then Abram fell on his face, and God talked with him, saying: “No longer shall your name be called Abram, but your name shall be Abraham; for I have made you a father of many nations. I will make you exceedingly fruitful; and I will make nations of you, and kings shall come from you. And I will establish My covenant between Me and you and your descendants after you in their generations, for an everlasting covenant, to be God to you and your descendants after you. Also I give to you and your descendants after you the land in which you are a stranger; all the land of Canaan, as an everlasting possession, and I will be their God. (Genesis 17:3-9)
How does this happen, and who are the heirs of Abraham. The point Paul makes in Romans 4 is that it is not a matter of law, or of works such as circumcision. It is not even a matter of being a Jew (for Abraham was neither a Jew, nor circumcised when the promise was first made). Rather, it is a matter of God's grace and is received by faith:
For the promise that he would be the heir of the world was not to Abraham or to his seed through the law, but through the righteousness of faith. For if those who are of the law are heirs, faith is made void and the promise made of no effect, because the law brings about wrath; for where there is no law there is no transgression. Therefore it is of faith that it might be according to grace, so that the promise might be sure to all the seed, not only to those are of the law, but also to those who are of the faith of Abraham, who is the father of us all. (Romans 4:13-15)From beginning to end, it is all about faith — believing God. As it was for Abraham, so it is for us:
He did not waver at the promise of God through unbelief, but was strengthened in faith, giving glory to God, and being fully convinced that what He had promised He was also able to perform. And therefore “it was accounted to him for righteousness.” Now it was not written for his sake alone that it was imputed to him, but also for us. It shall be imputed to us who believe in Him who raised up Jesus our Lord form the dead, who was delivered up because of our offenses, and was raised because of our justification. (Romans 4:20-25)Through faith in Jesus Christ, we are not only made right with God, but we also become the heirs of what God promised Abraham. Because of Jesus, through faith in Him, we are made heirs to the world. That is why, as Paul later said,
The earnest expectation of the creation eagerly waits for the revealing of the sons of God. For the creation was subjected to futility, not willingly, but because of Him who subjected it in hope; because the creation itself also will be delivered from the bondage of corruption into the glorious liberty of the children of God. (Romans 8:19-21)Through faith in Jesus Christ, we are made heirs to the world, along with faithful Abraham, and all of creation waits for the full manifestation of this inheritance.