Exodus 35:2-3

35:2 In six days work may be done, but on the seventh day there must be a holy day for you, a Sabbath of complete rest to the Lord. Anyone who does work on it will be put to death. 35:3 You must not kindle a fire in any of your homes on the Sabbath day.”

Numbers 15:35

15:35 Then the Lord said to Moses, “The man must surely be put to death; the whole community must stone him with stones outside the camp.”