8 “Remember the sabbath day, to keep it holy. 9 Six days you shall labor, and do all your work; 10 but the seventh day is a sabbath to the Lord your God; in it you shall not do any work, you, or your son, or your daughter, your manservant, or your maidservant, or your cattle, or the sojourner who is within your gates; 11 for in six days the Lord made heaven and earth, the sea, and all that is in them, and rested the seventh day; therefore the Lord blessed the sabbath day and hallowed it. (Exodus 20:8-11)
12 “‘Observe the sabbath day, to keep it holy, as the Lord your God commanded you. 13 Six days you shall labor, and do all your work; 14 but the seventh day is a sabbath to the Lord your God; in it you shall not do any work, you, or your son, or your daughter, or your manservant, or your maidservant, or your ox, or your donkey, or any of your cattle, or the sojourner who is within your gates, that your manservant and your maidservant may rest as well as you. 15 You shall remember that you were a servant in the land of Egypt, and the Lord your God brought you out thence with a mighty hand and an outstretched arm; therefore the Lord your God commanded you to keep the sabbath day. (Deuteronomy 5:12-15)
As you can see from the passages of Sacred Scripture, above, the Jews were commanded to keep the Sabbath for two reasons: to commemorate God’s rest on the seventh day of creation and to commemorate God liberating the Jews from their slavery to Egypt on a Saturday. As I see it, the first reason only establishes a work-rest pattern of six days of work followed by one day of rest without tying that day of rest to a particular day of the week. It is the second reason, which is of particular interest to Jews, that ties the day of rest to Saturday.
God liberating the Jews from their slavery to Egypt prefigured a far greater liberation to come, namely, God liberating mankind from their slavery to sin and death through the resurrection of Jesus Christ, which occurred on a Sunday. It makes sense that Christians would suppress the commemoration of the lesser Saturday liberation in favor of the greater Sunday liberation as their weekly day of rest.