John Calvin Commentary Genesis 31:53

"The God of Abraham, and the God of Nahor, the God of their father, judge betwixt us. And Jacob sware by the Fear of his father Isaac." — Genesis 31:53 (ASV)

The God of Abraham. It is indeed rightly and properly done that Laban should adjure Jacob by the name of God. For this is the confirmation of covenants: to appeal to God on both sides, so that He may not allow treachery to go unpunished. But he sinfully blends idols with the true God, between whom there is nothing in common.

Thus, truly, people involved in superstitions are accustomed to indiscriminately confuse sacred things with profane things, and human inventions with the true God. Laban is compelled to give some honor to the God of Abraham, yet he remains immersed in his own idolatrous pollution; and, so that his religion might not appear inferior, he gives it the appearance of antiquity. For in calling Him the God of his father, he boasts that this God was handed down to him from his ancestors.

Meanwhile, Jacob does not swear superstitiously. For Moses expressly declares that he swore only by the fear of Isaac; from which we learn that he did not agree to the preposterous form of oath dictated by his father-in-law—not as too many do, who, to gain the favor of the wicked, pretend to be of the same religion as them. But once the only God is made known to us, we wickedly suppress His truth, unless by its light all the clouds of error are dispersed.