As recently pointed out to me, there's some drama in this story that I've never noticed before, because of the way I was educated about the story.
As a kid in pre-school Bible Class, when you first start learning about Abraham and Isaac, you learn about Isaac before any of the other potential heirs. So when as an adult you actually read the book of Genesis, and you learn of a promised son, you automatically know it's going to be Isaac, and there's therefore no drama involved in reading the story about the other potential heirs. But if you were just reading the story for the first time without any fore-knowledge or preconceived notions, you see something like the following, a summary by Warren Rogers of material by one Dr. Rendsburg:
III. The Abraham story brings a host of potential heirs into the picture.I think it's good to introduce small children to interesting Bible stories, but this makes me wonder if we're not short-circuiting the educational process sometimes by "jumping to the chase". I have no solutions to this issue; I'm just making an observation.
A. First, we are directed to focus attention on Lot, but he is a nephew. Thus, we ask ourselves: Can he count as offspring? Perhaps, but then Lot departs in Genesis 13.
B. We next are introduced to Eliezer, an adopted son (to be discussed further). Is he the one? The answer is no, because as soon as Eliezer is introduced in Genesis 15, We are told that he will not be Abraham's heir.
C. At last, after much travail, Abraham gains a natural born son-Ishmael, son of Hagar, a servant woman presented to Abraham by Sarah.
D. But wait, in Genesis 21 another son is born to Abraham. Isaac, son of Sarah, confirming the more specific promise made to Abraham in Genesis 17 that Sarah would bear him a son---especially noteworthy.