EXODUS 31:13
Speak thou also unto the children of Israel, saying, Verily ye shall keep my sabbaths: for it is a sign between me and you throughout your generations; that ye may know that I am the LORD which sanctify you.Speak thou also unto the children of Israel, saying, Verily ye shall keep my sabbaths: for it is a sign between me and you throughout your generations; that ye may know that I am the LORD which sanctify you.