Moses returns to Egypt
Before Moses returned to Egypt he saw God in a burning bush. God had a covenant with Abraham that passed down to Moses telling him to bring the Egyptians to the promise land. When Moses was with God, God had showed him miracles to perform to the people so they would know God was with him.
When Moses went back to Jethro he told him that he wanted to go back to his own people to see if any of them were still alive. Jethro told him to go, The Lord told him to perform the wonders that he given him the power to do for the pharaoh when he gets to Egypt. The Lord made sure he hardened the Pharaohs heart so he wouldn't let the people go