Problem: Why didn’t God wait until he brought them into the Promised Land before he initiated the Sabbath?
Solution: The Egyptians used a ten day week. The Jews probably were not familiar with a seven day week. Therefore, once God pulled them out of Egypt, he was trying to reprogram them to his view of the world. In other words, God was saying, “Let me put you into the world that I created.”
“And it came to pass, that on the sixth day they gathered twice as much bread, two omers for one man: and all the rulers of the congregation came and told Moses. (Ex 16:22)”