What does Genesis 26:1 mean?
Isaac's experiences in Genesis 26 parallel those of Abraham, as described both in Genesis 12 and particularly in Genesis 20—21. In both instances, lies are told about a marriage out of selfishness and fear. Some scholars suggest this is a different version of the same events between Abraham and Abimelech, as told in chapter 20. Others, however, insist the two stories are separate and meant to show that God would be faithful to Isaac just as He had been faithful to Abraham.In any case, this verse makes clear that this famine is not the same one that drove Abraham and Sarah to Egypt in Genesis 12. This is a separate time of hardship. In the following verse, the Lord will tell Isaac explicitly not to go to Egypt in search of food. Instead, Isaac made his way to Gerar, a land ruled by Abimelech, king of the Philistines, to find more fertile territory.
Though not all scholars agree, most believe this Abimelech is not likely to be the same one Abraham interacted with. Approximately 90 years have passed since that event. It's possible "Abimelech" may have been a title—like "Pharaoh" or "Caesar"—rather than a personal name. The same might be true of the name of the army commander (Genesis 21:22; 26:26), or these might be names passed from fathers to sons.
This Abimelech is said to be king of a people called "Philistines." These Philistines, apparently, are not the same group that will later plague Israel. The title seems to be regional, not ethnic, and implies the people living in a certain area.