Genesis 21

The next chapter presents the closing scene in this series. The child and heir of promise is given; the child of flesh is dismissed. All now is settled according to God. Whatever inconsistent with His grace had been allowed before must disappear. Hagar the slave must depart, and the child that was not of promise must be gone. Jehovah can no longer tolerate that the child of flesh shall be with Isaac and Sarah in the house of Abraham.
Remarkable to say, while the goodness of God fails not to care for Hagar, Ishmael too in His providence is seen winding up the whole scene. Abimelech comes in, seeking a covenant with the very man whose failure must have surprised and stumbled him not so long before. Abimelech, with Phichol the chief captain of his host, owns God to be with Abraham in all that he did, adjures him to show favor to his race, and stands now reproved for the wrong of his servants. The Gentile king in short craves the countenance and protection of Abraham, “who planted a grove,” as we are told here, “in Beersheba, and called there on the name of Jehovah the everlasting God.”
It is clear therefore that here we behold the heir of the world in figure brought in. It is not a question yet of introducing deeper relations; nevertheless it is the heir not merely of the land of Palestine but of the world that comes before us here. Consequently Jehovah is presented to us in the character not before named of the everlasting God (El-olam). This fitly terminates the series, and brings us down to another type of the millennial day. It is then that the Gentiles seek the protection of the faithful; it is then that Jehovah will show Himself the God of ages, the guardian and blesser of the true Heir; it is then that pretensions of flesh and law will be forever put aside, and the promises will have their full course to His glory who gave them. This again concludes, as it would appear, in a way similar to the former section. We are carried forward to the millennial day.