The mountains quaked at the presence of Yahweh, Even yon Sinai at the presence of Yahweh, the God of Israel.
And that is by no means all that is proved by this reference.  It effectively DENIES the critical canard that Yahweh was a Canaanite god which Israel adopted after they conquered the Promised Land.  It reflects the great truth that God did indeed bring Israel out of Egypt, that he established the covenant with them at Sinai, and that God actually performed all the wonders that are attributed to Him in the Five Books of Moses.