We have Abram's family covenant. God reveals Himself—appeared to him—as the Almighty God; He was known to him by this name, see Ex. 6. A covenant between God and him, to multiply him. And God talked with him—he on his face; covenant with him—father of many nations—and kings—a God to him and his seed after him—the land and their God. All this forever, without condition, and his name changed for the covenant. Here, being a pilgrim, and continuing so, God is not ashamed to be called, and to lay the basis of being called, his God. The covenant of circumcision given to be kept—true circumcision to us by Sarah, the new covenant—he shall become father of nations, at least she shall be mother of them, even of kings. Howbeit, as Abraham's seed, but before this covenant, and after the flesh, Ishmael should become a great nation, but that was all of him—the son of the new covenant was joy; God left Abraham and went up, and Abraham kept the covenant, and with his house was circumcised.
This chapter, though with an important break, goes on to the end of chapter 21. We have again quite a new presentation of the way of God in the promises—it begins all afresh. Jehovah lays a new basis—Jehovah comes and reveals Himself by His name of relationship to Abram—chapters 15 and 16 were all within the circumscribed sphere of covenant lordship—He is simply the Lord Jehovah. We have now the father of nations consequently brought out—the heir promised by Sarah—the new covenant—and the separation of His people's family by circumcision—His fellowship with Abraham as His friend—His revealing His counsels and mind to him—Abraham's intercession—God's judgment of Sodom, where Lot, or the earthly-minded remnant was, yet who were of Abraham—for God remembered him and saved Lot—and here there is the break I spoke of.
The end of chapter 19 gives the posterity historically of Moab and Ammon; Abraham was up above, out of the judgments—not escaped from them. In chapter 17 we have God in His own supremacy—in chapters 18 and 19 the Lord in His covenant actings in promise and judgment—chapter 17 is the proper revelation of God to Abraham as such, and bringing him, and his family, into covenant with Him because they were his family.