Genesis 31:51-53

International Children’s Bible

⁵¹ Here is the pile of rocks that I have put between us. And here is the rock I set up on end. ⁵² This pile of rocks and this rock set on end will remind us of our agreement. I will never go past this pile to hurt you. And you must never come to my side of them to hurt me. ⁵³ The God of Abraham is the God of Nahor and the God of their ancestors. Let God punish either of us if we break this agreement.”

So Jacob made a promise in the name of God. This was the God of his father Isaac.