Exodus 31:13-16 King James Version (KJV)
13 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.
14 Ye shall keep the sabbath therefore; for it is holy unto you: every one that defileth it shall surely be put to death: for whosoever doeth any work therein, that soul shall be cut off from among his people.
15 Six days may work be done; but in the seventh is the sabbath of rest, holy to the Lord: whosoever doeth any work in the sabbath day, he shall surely be put to death.
16 Wherefore the children of Israel shall keep the sabbath, to observe the sabbath throughout their generations, for a perpetual covenant.