Exodus 6:7

6:7 I will take you to myself for a people, and I will be your God. Then you will know that I am the Lord your God, who brought you out from your enslavement to the Egyptians.

Exodus 10:2

10:2 and in order that in the hearing of your son and your grandson you may tell how I made fools of the Egyptians and about my signs that I displayed among them, so that you may know that I am the Lord.”