Moses was called by God in the third and fourth chapters of Exodus.

........It includes the burning bush; God revealing Himself to Moses and His plans for delivering Israel.

............It tells of how Moses hesitated and God permitting Aaron to help him.

.................We see the power of Moses' rod where he performed miracles.

So God not only manifested Himself to Moses as the Covenant-keeping God; but also as the miracle-working God.