The Hebrew paragraph divisions inspired by the Holy Spirit are:
Gen 18:1-19:38 s Abraham’s intercession and the overthrow of Sodom and Gomorrah
Gen 20:1-18 s Abimelech takes but then restores Sarah, Abraham’s wife
Gen 21:1-21 p Isaac becomes Abraham’s heir when he is weaned
Gen 21:22-34 p Abimelech and Abraham make a covenant of peace
Gen 22:1-19 p Abraham and the offering of Isaac
Gen 22:20-24 p The seed of Nahor
This parashah forms its own chiastic structure:
1a) Gen 18:1-33, The seed of Abraham promised (Isaac through Sarah);
1b) Gen 19:1-38 s, The judgment of Sodom and Gomorrah for sin;
1c) Gen 20:1-18 s, Abimelech and Abraham;
central axis) Gen 21:1-21 p, Isaac, the seed of promise, the heir of Abraham;
2c) Gen 21:22-34 p, Abimelech and Abraham;
2b) Gen 22:1-19 p, The Akideh: the father offers his only son, the promised seed;
2a) Gen 22:20-24 p, The seed of Nahor.
What is amazing to me is the B pair. They do not at first seem to match. But look: in the 1b pair, the destruction of Sodom and Gomorrah is reveals the judgment for sin … which is wrath. In the 2b pair, the prophetic picture of the father offering up his only son (Gen 22:2), the promised seed, reveals the sacrifice for sin … which is mercy.
They do in fact match, because the sin of man, which justice requires to be judged, calls forth from God, the mercy of God, which love requires the sacrifice for sin of Himself!