Exodus 35:1-3

And Moses gathered all the congregation of the children of Israel together, and said unto them, These are the words which the LORD hath commanded, that ye should do them. Six days shall work be done, but on the seventh day there shall be to you an holy day, a sabbath of rest to the LORD: whosoever doeth work therein shall be put to death. Ye shall kindle no fire throughout your habitations upon the sabbath day.