Exodus 34:21 Six days you shall work, but on the seventh day you shall rest; in ploughing time and in harvest you shall rest.
When God set the law about resting on the seventh day it was not something that could be changed over time but something that was set throughout time!
The Ten Commandments were written on stone tablets so that they lasted for as long as possible. God wants us to remember His law continually.
We all come up with various excuses how we can do some work on the seventh day, but God reminds us here that there are no excuses!