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 swearing; nor is it of any consequence that the pronunciation slightly varies from grammatical correctness, which in proper names is not very nicely observed. In fact, Moses does not restrict the etymology to the well, but comprises the whole covenant. I do not, however, deny that Moses might allude to the number seven [1]

Footnotes

1 - As the word sv' means both an oath and the number seven, room is left for this difference of interpretation. Calvin seems, however, to allude to a notion not uncommon among learned men, that as oaths were often made before seven witnesses, which perhaps the seven lambs represented, Abraham might have this number as well as the oath in his mind, when he called the well Beer-sheba. -- Ed

He called that place Beer-sheba - באר שבע Beer-shaba, literally, the well of swearing or of the oath, because they both sware there - mutually confirmed the covenant.

Wherefore he called that place Beersheba,.... Either Abraham or Abimelech, or both, called it so; or it may be read impersonally, "therefore the place was called Beersheba" (t), for two reasons, one implied, the other expressed; one was, because of the seven lambs before mentioned; so the Targum of Jonathan,"and therefore he called the well the well of seven lambs;''"Beer" signifying a well, and "sheba" seven; the other, and which is more certain, being expressed, is as follows:
because there they sware both of them; by the living God, to keep the covenant inviolably they had made between them.
(t) "vocatus", V. L. Calvin, Piscator.

From this circumstance, the place where it occurred received the name שׁבע בּאר, i.e., seven-well, "because there they sware both of them." It does not follow from this note, that the writer interpreted the name "oath-well," and took שׁבע in the sense of שׁבעה. The idea is rather the following: the place received its name from the seven lambs, by which Abraham secured to himself possession of the well, because the treaty was sworn to on the basis of the agreement confirmed by the seven lambs. There is no mention of sacrifice, however, in connection with the treaty (see Genesis 26:33). נשׁבּע to swear, lit., to seven one's self, not because in the oath the divine number 3 is combined with the world-number 4, but because, from the sacredness of the number 7, the real origin and ground of which are to be sought in the number 7 of the work of creation, seven things were generally chosen to give validity to an oath, as was the case, according to Herodotus (3, 8), with the Arabians among others. Beersheba was in the Wady es-Seba, the broad channel of a winter-torrent, 12 hours' journey to the south of Hebron on the road to Egypt and the Dead Sea, where there are still stones to be found, the relics of an ancient town, and two deep wells with excellent water, called Bir es Seba, i.e., seven-well (not lion-well, as the Bedouins erroneously interpret it): cf. Robinson's Pal. i. pp. 300ff.

Beer - sheba - That is, the well of the oath, in remembrance of the covenant that they sware to, that they might be ever mindful of it.