And Abraham said, I will swear. Although he had the stronger claim of right, he yet refuses nothing which belonged to the duty of a good and moderate man. And truly, since it is becoming in the sons of God to be freely ready for every duty; nothing is more absurd, than for them to appear reluctant and morose, when what is just is required of them. He did not refuse to swear, because he knew it to be lawful, that covenants should be ratified between men, in the sacred name of God. In short, we see Abraham willingly submitting himself to the laws of his vocation.

And Abraham said, I will (k) swear.
(k) So that it is a lawful thing to take an oath in matters of importance, to justify the truth, and to assure others of our sincerity.

And Abraham said, I will swear. Sensible of the many favours he had received from Abimelech in times past, and was still indulged with, he very readily agreed to his proposal; and the rather, as he knew by the vision between the pieces, that it would be four hundred years before his posterity should be put into the possession of the land of Canaan; and therefore could take an oath that neither he, nor his son, nor his grandson, should be injured or dispossessed.