Ezekiel 20:12, 20-21

Also I gave them My sabbaths to be a sign between Me and them, that they might know that I am the LORD who sanctifies them.

Sanctify My sabbaths; and they shall be a sign between Me and you, that you may know that I am the LORD your God.’ But the children rebelled against Me; they did not walk in My statutes, nor were they careful to observe My ordinances, by which, if a man observes them, he will live; they profaned My sabbaths. So I resolved to pour out My wrath on them, to accomplish My anger against them in the wilderness.