Exodus 35:1-3

Young's Literal Translation

35 And Moses assembleth all the company of the sons of Israel, and saith unto them, `These [are] the things which Jehovah hath commanded -- to do them:

² Six days is work done, and on the seventh day there is to you a holy [day], a sabbath of rest to Jehovah; any who doeth work in it is put to death;

³ ye do not burn a fire in any of your dwellings on the sabbath-day.'