What does Exodus 3:12 mean?
Moses has responded to God's commission to lead Israel's exit from Egyptian slavery with doubt and objections. God answers the doubt of Moses with the promise of His own presence. This echoes the sentiments of New Testament writers such as Paul, who noted, "If God is for us, who can be against us?" (Romans 8:31).God also gives Moses the first of many signs meant to confirm this message. Moses is promised that he will successfully return with God's people to the very mountain where he is standing. Both promises—Israel's liberation and their return to this location—will be fulfilled later in the book of Exodus. God would certainly be with Moses when he returns to Egypt. The many plagues which will take place, through Moses' prophetic announcements, will be further signs from God that it is His divine judgment coming down upon the Egyptians.
Horeb and Mount Sinai were the same area. Sinai will be the location where Moses receives the Ten Commandments (Deuteronomy 4:10, 15; 5:2; 9:8; 18:16). Generations later, Elijah will escape to this same area after defeating the prophets of Baal and running away from Jezebel (1 Kings 19).