"Some say If There is no record of seventh day Sabbath observance from its institution in Genesis 2:1-3 until we reach the Jews in the Book of Exodus. God’s commandments never existed prior to Mount Sinai.
TRUTH: If that argument were applied to the other nine 
commandments, it would mean that all those men between Adam and Moses were liars, thieves and profaners of the Lord’s name because we cannot find where the Lord ever told them not to do these things! Centuries before Moses, God judged His people by His law.
Because that Abraham obeyed my voice, and kept my charge, my commandments, my statutes, and my laws. Genesis 26:5."
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