Exodus 16:23; Exodus 31:15; Exodus 35:2

Exodus 16:23

23 then he said to them, "This is what the LORD meant: Tomorrow is a sabbath observance, a holy sabbath to the LORD . Bake what you will bake and boil what you will boil, and all that is left over put aside to be kept until morning."

Exodus 31:15

15 'For six days work may be done, but on the seventh day there is a sabbath of complete rest, holy to the LORD ; whoever does any work on the sabbath day shall surely be put to death.

Exodus 35:2

2 "For six days work may be done, but on the seventh day you shall have a holy day, a sabbath of complete rest to the LORD ; whoever does any work on it shall be put to death.