When did God first institute an organized system of worship?
God first instituted an organized system of worship at Mount Sinai, when Israel was gathered before Him after the Exodus and the completion of the 430 years. Scripture indicates that from Genesis 1 until Exodus 20 there were no written do’s and don’ts and no God-instituted worship until that point.
Les explains that after another 215 years, Moses led the children of Israel out of Egypt, the 430 years were completed, and the nation was gathered around Mount Sinai. At that point God was getting ready to do something totally different than He had ever done before. From Genesis 1 until Exodus 20, there were never any written do’s and don’ts from God concerning what men could and could not do, and there had not been one single item of God-instituted worship until they arrived there. People likely brought sacrifices, but so far as having an organized system of worship, there had been none.