Exodus 35:1-3

1 Then Moses gathered all the congregation of the children of Israel together, and said to them, "These are the words which the Lord has commanded you to do:
2 Work shall be done for six days, but the seventh day shall be a holy day for you, a Sabbath of rest to the Lord. Whoever does any work on it shall be put to death.
3 You shall kindle no fire throughout your dwellings on the Sabbath day."