Exodus 31:13-14

13“Now as for you, speak to the sons of Israel, saying, ‘1You must keep My Sabbaths; for this is 2a sign between Me and you throughout your generations, so that you may know that I am the Lord who sanctifies you.

14Therefore you are to keep the Sabbath, for it is holy to you. 3Everyone who profanes it must be put to death; for whoever does any work on it, that person shall be cut off from among his people.