Exodus 34:8-10

8And Moses made haste, and bowed his head toward the earth, and worshipped. 9And he said, If now I have found grace in thy sight, O Lord, let my Lord, I pray thee, go among us; for it is a stiffnecked people; and pardon our iniquity and our sin, and take us for thine inheritance.

10And he said, Behold, I make a covenant: before all thy people I will do marvels, such as have not been done in all the earth, nor in any nation: and all the people among which thou art shall see the work of Yhwh: for it is a terrible thing that I will do with thee.