Isaac is born—here is indisputable, historical reality as evidence that God gives life to the dead. Also, that we live on through our descendants is a witness to God giving everlasting life. Hagar and Ishmael are sent away as a practical necessity, but also as another historical parallel to the human condition and God’s saving work (see Paul’s reference to this in Galatians 4:21-31).
Abimelech appears again, this time wanting to make a covenant with Abraham. Notice how Abraham never wavers from his consciousness and practice of sojourning here: his physical life is like his tent; Abraham looks toward a better dwelling place, a regenerated body and recreated universe (Hebrews 11:8-12).