When we correlate Genesis 15, Genesis 22, Romans 4, and James 2, we will come to understand that there is no tension whatsoever between Paul’s view of faith and works over against that of James. Both appeal to how Abraham’s faith in Genesis 15 is accounted for righteousness, but both in fact go beyond that.
Like Paul, James affirms that Abraham’s faith in Yahweh’s promise was counted as righteousness (i.e. in Genesis 15, when God made the initial promise of seed). He affirms that within the framework of stating that Abraham was justified by works when he offered up Isaac on the altar (Gen 22, frequently referred to as the akedah). The point he makes is that the faith of Abraham (which Yahweh counted as righteousness) was active, and that it was completed by action. The offering of Isaac, says James, fulfilled the Genesis 15 statement that Abraham believed God, and it was counted to him as righteousness.
But doesn’t Paul put an opposition between faith and works where James does not? Yes and no. Paul puts an opposition between faith and works of Torah, but he most emphatically does not negate the need for faith to be active and persevering. Indeed, although in Romans 4 Paul is not explicit regarding the offering up of Isaac as James is in James 2, nonetheless the events of Genesis 22 are pretty clearly in his mind as he progresses to the end of the chapter. He typifies Abraham as the one who believes in the God who not only calls into existence the things that do not exist, but also gives life to the dead (Rom 4:17).
And while he aptly applies that death to the state of Abraham’s body and Sarah’s womb (Rom 4:19), it is surely impossible to leave out Genesis when he continues in verses 20–21, stressing that no distrust made Abraham waver concerning the promise of God, but grew strong in faith as he gave glory to God.
That language is not the language of a nanosecond affirmation, but of a commitment of faith over time, in the face of increasing obstacles; and moreover, the call of Genesis 22 is precisely a call to faith in that same promise, since it is precisely the object of promise, Isaac, whom Abraham is being called upon to offer up as an ascension offering.
Further, Paul culminates his argument by tying Abraham’s faith to ours, saying that this faith of Abraham we share “will be counted to us who believe in him who raised from the dead Jesus our Lord, who was delivered up for our trespasses and was raised on account of our justification.” The climax of death and resurrection in Abraham’s life is not the birth of Isaac, but rather his offering and figurative resurrection. (Hebrews credits Abraham’s faith by noting that he offered up Isaac in faith, believing that God was able to raise him up, which in fact he did.) A few chapters later, Paul echoes the akedah and applies it to God the Father: “He who did not spare his own son, but gave him up for us all, how will he not also with him graciously give us all things?”
Paul denies Abraham was justified by works (Rom 4:2ff), while James affirms that Abraham was justified by works (Jam 2:21). If the two mean the same thing by the phrase, they are in direct contradiction. But of course that is not the case. What James affirms in substance is that faith is active and is fulfilled in action—genuine faith is faithful. And Paul affirms the same thing: even in the face of a test that required him to sacrifice the object of the promise in which he believed, Abraham still clung to the promise and believed God, a belief in Yahweh that required faith that he would raise the dead.
That is James’ version of “justification by works,” and Paul is completely fine with that. Indeed, Paul elsewhere is very explicit about active perseverance in the life of faith being indispensable to arrival at a final reward. (E.g. if you live according to the flesh you will die, but if by the Spirit you kill the deeds of the body, you will live and be granted ultimate glory—Rom 8:12ff.; the one who sows to the flesh will reap eternal corruption, but the one who sows to the Spirit will from the Spirit reap eternal life—Gal 6:7–8.)
I do not intend here to go into full depth regarding what Paul is referring to when he speaks of works over against faith in Romans 4, but suffice to say that the whole discussion of Abraham follows upon a denial that justification is through the works of a law that would exclude Gentiles, since God is not the God of Jews only but also of Gentiles (Rom 3:27–31). He is pointing his fellow Jews away from an unflagging hope in Torah toward a different unflagging hope: a hope in the resurrected Jesus, who is in fact Torah’s own goal (cf Rom 10:4). The issue is not whether faith requires faithfulness; the issue is that genuine faith is in the God who gives life to the dead, specifically as the Father of the crucified and resurrected Messiah our Lord—a fact that (according to Paul) has huge implications for the permanence of Torah.