Genesis 31:49-53
49 It was also called Mizpah, because he said, “May the Lord keep watch between you and me when we are away from each other.
50 If you mistreat my daughters or if you take any wives besides my daughters, even though no one is with us, remember that God is a witness between you and me.”
51 Laban also said to Jacob, “Here is this heap, and here is this pillar I have set up between you and me.
52 This heap is a witness, and this pillar is a witness, that I will not go past this heap to your side to harm you and that you will not go past this heap and pillar to my side to harm me.
53
May the God of Abraham and the God of Nahor, the God of their father, judge between us.”
So Jacob took an oath in the name of the Fear of his father Isaac.