So that place was called Beersheba, because it was there that the two of them swore an oath.
31. Wherefore he called that place Beer-sheba . Moses has once already called the place by this name, but proleptically. Now, however, he declares when, and for what reason, the name was given; namely, because there both he and Abimelech had sworn; therefore I translate the term ‘the well of swearing.’ Others translate it ‘the well of seven.’ But Moses plainly derives the word from...
We have here an account of the treaty between Abimelech and Abraham, in which appears the accomplishment of that promise (Gen 12:2) that God would make his name great. His friendship is valued, is courted, though a stranger, though a tenant at will to the Canaanites and Perizzites. I. The league is proposed by Abimelech, and Phichol his prime-minister of state and general of his army. 1.
Commenting on Genesis 21:22-32
And Abraham sojourned in the Philistines' land many days. Even many years, days being sometimes put for years; having entered into covenant with Abimelech, the king of the country, and settled a good correspondence with him, and having his friendship and good will, which commanded respect from his subjects, Abraham sojourned very quietly and comfortably for many years, chiefly at Beersheba; the Jewish writers say...