The visits of Abraham to Egypt in Genesis Ch. 12 and to the Philistines in Ch. 20 are notable first for their similarities and then for their differences. The stories begin the same way. Abraham arrives with his beautiful wife Sarah and presents her as his sister. Immediately, the border guards confiscate the woman and bring her to the king (Pharaoh in Egypt, Abimelech among the Philistines) as a trophy. Then God punishes the king until he is forced to relinquish the woman.
What are the points of distinction between the two stories?
1) Pharaoh's punishments are delivered by an angel, whereas Abimelech receives a prophecy directly from God telling him to free the woman. That prophecy takes the form of a dialogue in which the king declares to God that he would never have taken her had he known that she was married.
2) Pharaoh's punishments are described as 'great plagues', indicating that they were visible. Abimelech was punished by the wombs of his womenfolk being barren, something that takes place internally.
3) Abraham did not bother explaining himself to Pharaoh after the ruse was discovered, but when Abimelech confronted him, he took the trouble to parse his own calculations and motivations.
4) Abraham leaves Egypt entirely behind but he develops a comfortable working relationship with the Philistines and even signs a peace treaty that is valid for four generations.
The conclusion seems clear. Pharaoh was running an evil society but Abimelech was leading a decent society. Prophecy is not possible for evil Pharaoh but is quite appropriate for Abimelech, a basically nice person. Abimelech can tell God truthfully that he would not ordinarily behave in that fashion.
Being a nice person running a decent society, Abimelech is entitled to an explanation from Abraham. Pharaoh is a lowlife who is not deserving of such consideration. Eventually, Abraham can come to terms with Abimelech sufficient to the formation of a diplomatic relationship encoded in treaty. Such concord is impossible with a Pharaoh.
Consequently, the plagues visited upon Pharaoh are public and conspicuous. His society is openly corrupt and the punishment fits the crime. Abimelech, however, has an outwardly civil society, with some subtle internal flaw. Its retribution is delivered in ways that do not present themselves to the casual observer. The flaw is deep; the reproof is beneath the surface, as well.
What, then, is this shortcoming that prevents the Philistine society from being a truly virtuous one? Abraham answers that himself when he says (Genesis 20:11): "Because I said [to myself] that there just is not the fear of the Lord in this place, and they might kill me over the matter of my wife."
There it is: civil society without fear of God. For all that it is vastly superior to the Egyptian model of grab-now-ask-later, Abraham argues that it still is fatally flawed because it has no ultimate limiting force. The Philistines have arrived at the strong sociological conclusion that their lives will be better if they treat each other with civility and respect each other's property rights. But they do it because it works, not because it's right. At some point, that will break down. Maybe a million dollars, maybe ten million; there is a point at which the person will make the grab and forget the principles. Abraham did not want to test their resolve with his wife, the world-class beauty.
In our final installment, we will apply these lessons to the latter-day Philistines of Samuel's day.