I find chapter 20 not only troubling, but mysterious; I'm not sure what to make of it. So let me deal with it by pointing to things in it that interested me and by raising questions.
Verse 1 of the chapter tells us that Abraham "journeyed from thence," but there is no referent for "thence" (shm): we don't know where Abraham is journeying from, but the text assumes that we do. Of course this is evidence of the redaction process, but if we take it as part of the text, as part of a whole, we can ask what it means in that text. What are we to make of the fact that we do not know where Abraham has come from when this story begins? Or does it begin from a situation, Abraham's situation in comparison to Lot's rather than from a place?
If we think broadly about the two stories and see the way in which each shows us a different kind of hospitable life, perhaps we can read this as saying that we see Abraham, who knows how to be hospitable, moving into potentially hostile company. He is entering a home where he cannot be assured of hospitality. That suggests that this chapter is about God's protection of Abraham when hospitality fails.
It is impossible to overlook the parallel between the story of this chapter and the story in Genesis 12:9-20. Verse 1 immediately makes the connection to the story in chapter 12 by using "journeyed" and "dwelled," translations of the same Hebrew verbs used at the beginning of the earlier story. The redactor wants us to know that he sees these stories as parallel; he is conscious of the existence of two stories and includes them both.
What might we get from comparing and contrasting the two stories?
- There, Abraham went all the way into Egypt. Here, he goes to the border of Canaan, but not into Egypt.
- There Sarai becomes became part of the royal harem. Here she doesn't get that far.
- There Abram explains the political reason for referring to Sarai as his sister. Here he explains why calling Sarah his sister wasn't a lie.
- In chapter 12, we don't know how the Pharaoh came to know that Sarai was Abram's wife. In this chapter, the Lord appears to Abimelech in a dream to tell him.
- The Pharaoh puts all of the blame on Abram. Abimelech accepts some of the blame.
- The Pharaoh immediately expelled Abram from Egypt. Abimelech allows him to choose the land he wishes.
- The Pharaoh is concerned with what has happened to him (12:18). Abimelech is concerned with what Abraham may have done to his nation.
- The earlier story is a foreshadowing of Israel's entrance, sojourn, and exodus from Egypt. Is this one also?
Abimelech's plea in verse 4, "Wilt thou slay also a righteous nation?" is very much like Abraham's plea for Sodom in Genesis 18:30-32.
Verse 7 is the only occurrence in Genesis of the word nabi, "prophet": God identifies Abraham as a prophet. (The word is used very sparingly in the Pentateuch, 12 times, with 8 of those times in Deuteronomy.) It strikes me as odd that it is important to this strange story that Abraham is a prophet.
An overall oddity is that in this chapter we see Abraham, who has already been shown to be a mighty warrior who can defeat multiple kings (chapter 14), afraid of one king, Abimelech—a king whom, as Word Biblical Commentary points out, Abraham has misjudged (2:72). Compare what God says about Abimelech in verse 6 with what Abraham thought about the country in verse 11.
And why does Abraham lie in verse 13 about using this ruse with Sarah "at every place where we shall come"? He's only done it once before.
In summary, Word Biblical Commentary is helpful once again: "This incident makes us realize that Abraham is not such a saint as we might have concluded from chap. 18, nor were all the inhabitants of Canaan so depraved as those who lived in Sodom" (2:75).
With chapter 21, we enter into more familiar territory, though that isn't to say that there are no difficulties.
The first story in the chapter is that of Isaac's birth and Ishmael's expulsion, and I think we have to read those two stories together: the birth of the covenant child means the expulsion of the child of the handmaiden. Can we think past twentieth-century sensibilities to see what the point is, and then, having done so, can we bring that point back in a way acceptable to our sensibilities?
Without trying to justify Sarah's anger or Abraham's complicity (nor deciding ahead of time that I understand that anger and complicity well enough to know what it means), one thing I see here is that covenant and promise are not the same. Verses 17-18 tell us that God will make a great nation of Ishmael, repeating the promise of Genesis 17:20: "I will make him a great nation." However, Genesis 17:21 adds: "But my covenant will I establish with Isaac." Though the promise of the covenant is that Abraham will be a great nation, that promise is not the same as the covenant. For Ishmael and Isaac each receives that same promise, but only Isaac receives the covenant.
So what is the covenant of Abraham? Is it "I will bless thee"? That seems to be the promise. Is it "Thou shalt be a blessing"? Isn't God saying that to be covenanted is to be blessed to be a blessing? Merely being blessed (Ishmael) is not enough and must be sent away. Being blessed to be a blessing remains.
The chapter ends with the covenant between Abimelech and Abraham. Is that to set up a contrast with the covenant that is to come in the next chapter, not only in the two covenants themselves, but the way in which they are established: Abraham offers sheep and oxen to Abimelech; he offers his son to God.