"Some have contended that the Sabbath was not instituted until the law was given to Moses at Mount Sinai.
---But there are serious difficulties in the way of this belief.
---In the second chapter of Genesis, after having given an account of the creation, the sacred historian says: "On the seventh day God ended his work which he had made: and he rested on the seventh day from all his work which he had made. And God blessed the seventh day and sanctified it; because that in it he had rested from all his work which God created and made."
---Now, if any part of this narrative is to be construed literally, the 
whole of it must be;
---and if we may not venture to deny or explain away the account which Moses has given of the creation, then we may not deny or explain away this unequivocal statement respecting the original institution of the Sabbath in Paradise.
***The blessing and sanctifying of the seventh day is mentioned in connection with the first seventh day in the order of time, and it is so mentioned as most forcibly to impress the reader that the Sabbath was then instituted." James White