James uses the examples of Abraham and Rahab to illustrate how faith and works go together. He also takes an incident from each of their lives to make his points: the one from the life of Abraham is his offering of his son Isaac on Mount Moriah and the one from the life of Rahab occurred just before her hometown of Jericho was destroyed by Israel in obedience to God.
Looking at those two examples, we can see several differences between them. First, Abraham was an established believer, having followed God for several decades, before being asked to obey in this unusual way. In contrast, Rahab was a new believer, just converted. So we can deduce from these examples that real faith shows appropriate works at each stage of its development.
Second, Abraham had entered the kingdom of God through receiving a profound, personal encounter when the God of glory appeared to him and called him to leave Ur and head away to an unknown country, depending only upon God for guidance. In contrast, Rahab had only heard reports of what God had done in Egypt forty years earlier when he delivered his people from bondage; in addition, she knew what the spies had told her. Yet the difference in their conversions did not mean that their faith would be without appropriate works.
Third, Abraham’s faith showed its reality in a very peculiar personal situation whereas Rahab’s faith showed its reality by identifying with the enemies of her people. In a sense, Rahab was only doing what Ruth would later do when she left the Moabites and adhered to the Israelites. We can say that Rahab only did, in her own way and time, what every Christian does when he or she begins serving the Lord – they leave the old way of life with its various ungodly features and join God’s people. In contrast, Abraham was placed in a very traumatic situation in which his faith was put to the severest of tests over a short period of time, and which seemed to be the opposite of everything God had said previously about the holy line descending through Isaac. Yet the point that James is making is that both of them showed by their responses that their faith was genuine.
Fourth, it could also be the case that the two examples selected by James were an indication to his readers to expect outsiders to join their communities. Both Abraham and Rahab were pagans when God called them, and those believers to whom James was writing should have been witnessing to Gentiles. It would have been encouraging for such to know that pagans can show true faith even when from such unlikely backgrounds.
Fifth, both Abraham and Rahab were challenged to act on their own when it came to faith. There were no other believers in Ur when God appeared to Abraham, although we know that Sarah would have believed soon after. And there were no other believers in Jericho when Rahab chose to identify herself with the God of Israel. True faith will stand by itself if it has to.