Exodus 31:13 in the King James Version
Speak thou also unto the children of Israel, saying, Verily my sabbaths ye shall keep: for it is a sign between me and you throughout your generations; that ye may know that I am the LORD that doth sanctify you.
Context
12 The LORD spoke to Moses, saying,
13 “Speak also to the children of Israel, saying, ‘Most certainly you shall keep my Sabbaths; for it is a sign between me and you throughout your generations, that you may know that I am the LORD who sanctifies you.
14 You shall keep the Sabbath therefore, for it is holy to you. Everyone who profanes it shall surely be put to death; for whoever does any work therein, that soul shall be cut off from among his people.