GEN836 … when Abraham took upon himself the mission of teaching mankind about the existence of God, he was not confident that his efforts would succeed until he had a natural son who, bound by the ethics of kibbud ov, [honor owed a father -AJL], would carry over his teachings to the later generations.  After years of childlessness, Abraham fully well realized that his disciples, Eliezer or Lot, would not be able to carry on after his death. Their resolve would not be able to withstand the pressures of the pagan culture. And so wearily and tragically Abraham complained to God, “What can you give me? For I go childless.” [this verse] It was only after a divine promise of a son that Abraham was consoled. And only after the birth of Isaac, God declared, “and Abraham will become a great and strong nation, all the nations of the world will praise themselves in him. For I know him, that which he will command his children and his family after him they shall keep the way of God to do righteousness and justice. Genesis 18:18-19.  Only the special authority which a father could expect from a son would assure the transmission of Abraham’s noble ideas for the coming generations.  BUILD 243-5