Why does the Arab world claim to be the true children of Abraham?
The Arab world claims to be Abraham's true children because it traces descent through Ishmael, Abraham's son by Hagar. In this context, the Koran is understood to assign the covenant promises to Ishmael rather than Isaac, so they regard themselves as rightful heirs and owners of the Holy Land.
Les explains that God had promised Abraham and Sarah a son for some fifty years, and through that promised son would come the nation of Israel in fulfillment of the covenant promises. But Abraham became impatient and followed the pagan custom of using a surrogate mother. Sarah suggested Hagar, their slave girl, and Abraham agreed, producing Ishmael—a natural son and a child of Abraham. That fleshly origin, Les says, is the conflict in the Middle East yet today. The Arab world says they are Abraham's true children because, as Les understands the Koran, it puts the covenant promises with Ishmael instead of Isaac. Therefore they feel they are the rightful owners of the Holy Land. Paul also writes that not all who are Israel are Israel, and that not because they are Abraham's seed are they all children; rather, in Isaac shall thy seed be called.