Genesis 21:24

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.