Let the punishment fit the crime, again.

"Observe the Sabbath, because it is holy to you. Anyone who desecrates it is to be put to death; those who do any work on that day must be cut off from their people." Exodus 31:14 "...Whoever does any work on the Sabbath day is to be put to death." Exodus 31:15

God also wanted people to be put to death for littering and for chewing on the left side of their mouths but he completely forgot to tell Moses.