There are many Protestants that will hold this verse up as proof positive that faith is not the substance of doing but rather the substance of believing only (sola fide) I even had one teacher walk right up to the edge of sayings that James erred in his teaching or had not perhaps read Paul when he wrote his letter or that James’ letter was an earlier more Judaistic Christianity which was then later refined by Paul…
that is until I pointed out to him that by his own confession both men were inspired and inerrant and thus could not be divergent in their meaning and so it was his understanding that had to be defective.
Ya I was Catholic back then too I just couldn’t admit it.
In fact it is Abraham who has walked with the Lord many years and shown his faith by his works again and again that The Lord then counts his believing of the promise of a son as righteousness. Our faith is the sine qua non of salvation but it is the beginning of our life in Christ not the end. It is not as though we are baptized and receive one confession and then are told to white knuckle it until death, that would be a strange faith indeed. Rather our actual righteousness is created in us by the faith in Christ which is ours by grace and grows in us all our lives and so we believe more and more as we grow in and cooperate with grace.
And that is of course exactly what we see with Abraham. He is old and Sarah is old and there is no good reason for him to believe this promise, but Abraham has come to know this God very well and he trusts him completely and so when God promises him a son and a progeny as the stars and that kings will come from him Abraham laughs for joy and believes God.
And of course. God counts that as righteousness.
Because it is.