Carl Friedrich Keil and Franz Delitzsch Old Testament Commentary

Abraham sojourned a long time there in the Philistines' land. There Isaac was probably born, and grew up to be a young man (Gen 22:6), capable of carrying the wood for a sacrifice; cf. Gen 22:19. The expression "in the land of the Philistines" appears to be at variance with Gen 21:32, where Abimelech and Phicol are said to have returned to the land of the Philistines. But the discrepancy is easily reconciled, on the supposition that at that time the land of the Philistines had no fixed boundary, at all events, towards the desert. Beersheba did not belong to Gerar, the kingdom of Abimelech in the stricter sense; but the Philistines extended their wanderings so far, and claimed the district as their own, as is evident from the fact that Abimelech's people had taken the well from Abraham. On the other hand, Abraham with his numerous flocks would not confine himself to the Wady es Seba, but must have sought for pasture-ground in the whole surrounding country; and as Abimelech had given him full permission to dwell in his land (Gen 20:15), he would still, as heretofore, frequently come as far as Gerar, so that his dwelling at Beersheba (Gen 22:19) might be correctly described as sojourning (nomadizing) in the land of the Philistines.