Exodus 31:12-16

12And Jehovah spake unto Moses, saying, 13Speak thou also unto the children of Israel, saying, Verily ye shall keep my sabbaths: for it is a sign between me and you throughout your generations; that ye may know that I am Jehovah who sanctifieth you. 14Ye shall keep the sabbath therefore; for it is holy unto you: every one that profaneth it shall surely be put to death; for whosoever doeth any work therein, that soul shall be cut off from among his people. 15Six days shall work be done, but on the seventh day is a sabbath of solemn rest, holy to Jehovah: whosoever doeth any work on the sabbath day, he shall surely be put to death. 16Wherefore the children of Israel shall keep the sabbath, to observe the sabbath throughout their generations, for a perpetual covenant.