The Word given to Abraham declared that his seed would be a stranger in a land that was not theirs. After the season of bondage, God would bring them out to go into the land that promised to Abraham.
The covenant promise to Abraham would produce the word that would give birth to Moses. Moses would eventually hear and obey God's voice and lead God's chosen people into the promised land.
We must understand that God does what He does for the express purpose of ensuring that He honors His Word. After leading His people to the wilderness, God gave them his commands which would also become know as the Law of Moses.