Exodus 31:16 Wherefore the children of Israel shall keep the Sabbath, to observe the sabbath throughout their generations, for a perpetual covenant.
God commanded Israel to Remember the Sabbath Day to keep it Holy. No work is to be done; it is to be a Day of Rest. Since God rested on the seventh day of Creation, human creatures are to remember in faith their Creator God. And rest. Setting apart the seventh day is a response of the people of faith. Most of the Jews were faithful in keeping that day apart from the other days of the week.
The principle of the week is still embedded in human culture as a measure of time. It is interesting, because every other measure of time and season (day, month, year, even hours, minutes and seconds) is based upon the sun and the moon, created nature. The week is not; it is based on only one thing: God’s Creation and God’s Word. The unbelieving world unknowingly acknowledges God by taking Sunday off, though atheists would not admit that.
Since the New Testament, The Day is no longer to be observed, because it is a shadow of things to come: it foreshadows Christ and the Eternal Rest He brings. God Himself abrogated this Commandment. Christ causes the shadow. Now that the real thing has come we no longer worship the shadow, but we worship the substance to which the shadow points. To continue to keep the Sabbath is a denial that Jesus has come and fulfilled the foreshadowing prophecy. “Keeping Sabbath” trusts works instead of Grace in Christ. It says, “Jesus is not the promised Messiah.” Jesus says, “The Son of Man is Lord of the Sabbath.”
Early Christians determined that the believing response to the Creation’s Principle is to set aside the eighth day as the day for pausing from regular work, in order to make time for the public proclamation of the Word and celebration of the Sacrament. And it is a regular reminder of the Resurrection. Therefore, Believers respond to the Gospel with weekly worship on the Lord’s Day, Sunday.