Two Reasons, One Day

Put the two versions side by side and the difference shows up immediately.

Exodus says remember the Sabbath day. The reason given is creation: six days of making, and rest on the seventh.

Deuteronomy says observe the Sabbath day. The reason given is Egypt: remember that you were a slave there, and that God brought you out.

Same day, two arguments. One says rest because that is the shape the world was made in. The other says rest because you are not property any more, and people who belong to someone else do not get to stop.

Both are in the text. Keeping only the first turns the day into a rule about the calendar. Keeping only the second turns it into a reward for effort.

Held together, they say something narrower. A week you cannot interrupt is worth looking at closely, and asking who exactly you think you belong to.