Genesis 21

1. We have in the ways and faithfulness of Jehovah in promise, His name brought out.
Then all the dealings historically are Elohim; Elohim had spoken, not man; Elohim, in mercy, heard the voice of the lad; Elohim could not allow the bondwoman's seed to inherit.
Note here how we have the origins gentium, no doubt in the family of Shem. The Ishmaelites, as is known, characterize whole countries to this day, but they were allied with Ham, and Egypt; here his mother and wife were Egyptians. Now that Isaac has his true place as sure and only heir, Abraham recognizes Jehovah, the God of the full future of purpose, the El o-lam (God everlasting). This helps to the khay-yey o-lam (life everlasting); Dan. 12:22And many of them that sleep in the dust of the earth shall awake, some to everlasting life, and some to shame and everlasting contempt. (Daniel 12:2). Only the now incarnate and glorified Christ gives other elements of it.
This chapter brings in the heir and that is clear enough; the fleshly heir is cast out, the seed of Hagar, only as Abraham's seed there is earthly blessing. The world recognizes Abraham as the one blessed of God, and here we come to earthly and so Jewish title, yet by the manifested seed.
33. This was a kind of pledge of the possession of the land, as also the title he gives Jehovah. He was Jehovah olam for a future day yet hidden, save in promise; Beersheba was literally the bounds of the land.
33, 34, is a sort of taking into possession of the land or earth, and the name of God refers to that; He is Jehovah, the El dam, the God of Might forever, for the yet hidden future.
Note this; the conduct of the believer—as under the blessing in the land wherein he is a stranger, not having so much as to set his foot on—and Isaac, not in the same strength of blessing, yields—in principle right and alike, but not exercising the same spiritual energy—not in the same power of blessing. Is it connected with what goes before?