So how do we fit what we know of Abraham, our first father in the faith, into this new way of looking at things?
If Abraham, by what he did for God, got God to approve him, he could certainly have taken credit for it. But the story we're given is a God-story, not an Abraham-story.
What we read in Scripture is, "Abraham entered into what God was doing for him, and that was the turning point. He trusted God to set him right instead of trying to be right on his own."
If you're a hard worker and do a good job, you deserve your pay; we don't call your wages a gift.
But if you see that the job is too big for you, that it's something only God can do, and you trust him to do it - you could never do it for yourself no matter how hard and long you worked - well, that trusting-him-to-do-it is what gets you set right with God, by God. Sheer gift.
David confirms this way of looking at it, saying that the one who trusts God to do the putting-everything-right without insisting on having a say in it is one fortunate man:
Fortunate those whose crimes are carted off, whose sins are wiped clean from the slate.
Fortunate the person against whom the Lord does not keep score.
Do you think for a minute that this blessing is only pronounced over those of us who keep our religious ways and are circumcised? Or do you think it possible that the blessing could be given to those who never even heard of our ways, who were never brought up in the disciplines of God? We all agree, don't we, that it was by embracing what God did for him that Abraham was declared fit before God?
Now think: Was that declaration made before or after he was marked by the covenant rite of circumcision? That's right, before he was marked.
That means that he underwent circumcision as evidence and confirmation of what God had done long before to bring him into this acceptable standing with himself, an act of God he had embraced with his whole life.