The following is my translation of Romans 4:
"What about Abraham? In the flesh he was the father of the Jewish nation but remember how he was made right with God? If it was his own acts of kindness that reconciled him and God then he would have had something to brag about but that was not God's way. For the Bible states that "Abraham trusted God, and God granted him right standing solely because of that trust." Now, when people work their paycheck isn't a gift but is earned but people are made right with God not because of something they have done but because of their trust in God who forgives His rebellious children.
David also said as much when he wrote about the happiness of those who are reconciled to God without earning it: "Oh, how happy are those whose rebellion is forgiven, whose crimes against God are wiped away. Yes, there is great excitement for those who have been forgiven by God."
Now is this great gift only for the Jewish people or is it for all people? Well, we have been talking about the fact that Abraham was reconciled to God because of his faith. But think about how this happened--Was Abraham declared to be in God's favor only after he was circumcised or was it before he was circumcised? Clearly, God accepted Abraham before he was circumcised!
Circumcision was only the sign that Abraham already trusted God and that God had already accepted him and looked upon him with favor--even before he was circumcised. So, Abraham is the spiritual father of those who have faith but have not been circumcised--they are in God's favor because of their faith--and Abraham is also the spiritual father of those who have been circumcised, but only if they have the same kind of faith Abraham had before he was circumcised.
Clearly God's promise to give the whole earth to Abraham and his descendants was based not on his obedience to the Mosiac law but on a right relationship with God that comes by belief and trust. If God's promise is only for those who obey the Mosaic law, then faith is not necessary and the promise is pointless. For the law always brings punishment on those who try to obey it (I mean, the only way to avoid breaking the law is to have no law to break!)
So the promise is received by faith. It is given as a free gift and we are all certain to receive it if we have the faith of Abraham whether or not we live according to the law of Moses for Abraham is the father of ALL who trust God. That is what the Bible means when God told him, "I have made you the father of many nations." This happened because Abraham believed in the God who brings the dead back to life and who creates new things out of nothing!
I mean even when there was no reason for hope, Abraham kept hoping--believing that he would indeed become the father of many nations. For God said to him, "that's how many descendants you will have!" and Abraham's faith did not weaken, even though, at about 100 years of age, he figured his body was as good as dead--and so was Sarah's womb.
But Abraham never wavered in believing God's promise. In fact, his trust grew stronger and this honored God. Abraham was absolutely certain that God is able to do whatever He promises and because of this belief and trust--God looked upon him with favor and when God did this, it wasn't just for Abraham's benefit, it was recorded for our benefit too, assuring us that God will also look upon us with favor if we trust in Him, the one who raised Jesus, our King, from the dead. Jesus was handed over to die because of our crimes against God but he was resurrected from the dead to reconcile us with God.