New Defender's Study Bible Notes
20:1 Gerar. Gerar was capital of the Philistine colony on the seacoast. The Philistines were descendants of Ham through Mizraim, and apparently were originally from Crete. Some centuries later, they all migrated to Canaan and became a strong coastal nation, inveterate enemies of Israel. The name Palestine came from them. The title of their kings at this time was Abimelech, similar to Pharaoh in Egypt.
20:2 my sister. How Abraham and Sarah could have entered into the same type of deception for which they had long before been rebuked in Egypt (Genesis 12:10-20) is hard to understand, but apparently the situation took them by surprise and they got trapped into the same old subterfuge before they realized it.
20:2 Abimelech. Abimelech was evidently a title, like Pharaoh in Egypt. Gerar was a prosperous Philistine settlement along the coast, near the Egyptian border, and Abraham must have journeyed there for business purposes.
20:7 a prophet. This is the first use of the word “prophet” or “prophecy” in Scripture. As the context indicates, its meaning is not primarily that of foretelling the future, but of being God’s spokesman, conveying His words by divine inspiration to man (compare II Peter 1:19-21). God exacts strong punishment on any who harm His prophets, even when they themselves are blameworthy (Psalm 105:15).
20:11 will slay me. The fact that Abimelech did not deny Abraham’s expressed charge indicates that his fears may well have been justified.
20:12 my sister. Sarah was Abraham’s half-sister. In the early centuries after the Dispersion, close marriages were often necessary, with very small tribal populations. This may have been especially desirable in godly families, in order to preserve faithfulness to God’s revelation and His purposes. As noted before, this situation was not harmful genetically until many harmful mutations could have accumulated in the nation’s genetic pool. By the time of Moses, this had apparently become a problem, and laws against incest were established.