How did Abraham come to have Ishmael by Hagar?
After roughly fifty years of waiting for the promised son, Abraham became impatient. Sarah first suggested using their slave girl Hagar as a surrogate mother, a pagan custom, and Abraham quickly agreed. From that fleshly idea came Ishmael, Abraham's natural son.
Les explains that God had promised Abraham and Sarah a son for about fifty years, and through that son would come the nation of Israel in fulfillment of the covenant promises. But Abraham grew impatient and delved back into the pagan custom of using a surrogate mother. Sarah thought of it first and suggested they have a son by their slave girl Hagar, and Abraham quickly agreed. From that fleshly idea came Ishmael, Abraham's natural son. Les notes this same conflict persists in the Middle East today, because the Arab world claims to be the true children of Abraham, and the Koran, as Les understands it, places the covenant promises with Ishmael rather than Isaac, so they feel they are the rightful owners of the Holy Land.