Observing the Sabbath day command in the 10 commandments is greatly misunderstood. The Sabbath day command was a sign of God's covenant with the nation of Israel (Ex. 31:13-17). In fact, the keeping of the Sabbath day command is the only one of the 10 commandments not renewed in the New Testament. Sunday worship is not the replacement of the Sabbath day command. Does the Sabbath day command have any relevance for the Christian today? Yes! The reality of the Sabbath day of rest is found in Christ (Col. 2:16-17).
