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.
Exodus 35:2
Surrounding context
35:1 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:
35:2 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.
35:3 You shall kindle no fire throughout your dwellings on the Sabbath day."