Isaac is the son of promise and the seed of Jesus and Ishmael wasn't. Isaac symbolizes the new covenant. Ishmael symbolizes the old covenant. Abraham asked Ishmael to leave his house not because he was mean but knew the new and old covenant cannot live under the same roof. Sarah is the mother of grace and freedom and symbolizes Zion. Hagar the mother of Ishmael and a slave symbolizes Mt. Sinai and the shackles of the Law. Abraham asked her to leave as well because grace and the law cannot live under the same roof. God in His love, compassion and mercy still took care of them and out of Ishmael begat Saudia Arabia and other great kingdoms around it.
