The Fourth Commandment
"Observe the Sabbath day, to keep it holy, as the Lord your God commanded you" (v. 12).
Question and answer 103 of the Heidelberg Catechism address the fourth commandment, which directs the people of God to sanctify the Sabbath day and rest (Deut. 5:12–15). The statements in the catechism about the meaning of this statute for Christians assume, along with the vast majority of Christian theological traditions, that the Christian Sabbath is celebrated on the first day of the week, otherwise known in Scripture as the Lord's Day (Rev. 1:10).
Some groups have been troubled by the keeping of the Lord's Day on the first day of the week, as Deuteronomy 5:12–15 specifies the seventh day of the week for Sabbath observance. Yet there are good reasons why the church has seen the need for a change in keeping the Sabbath under the new covenant. In the first place, first-day Sabbaths were not unheard of under the old covenant, so there was precedence for celebrating a day of rest on the first day even before the incarnation (Lev. 23:7, 15–21). More significant: "The Son of Man is lord even of the Sabbath" (Mark 2:28). With the advent of Jesus, there was a monumental change in redemptive history. The Sabbath can no longer be imagined without reference to the work of Christ. On the first day of the week, Jesus was raised for our justification (John 20:1–10; Rom. 4:23–25). So, the church, with good reason, has seen that the day of worship and rest should be celebrated on Sunday.
This change receives further confirmation when we consider that one of the purposes of the Sabbath under the old covenant was for the people to remember God's great act of salvation in the exodus from Egypt (Deut. 5:15). Since the work of Christ is an even greater redemption, it is appropriate to remember it on the Sabbath as well, and keeping the first day for this purpose helps ensure that we do not forget the resurrection. Moreover, this call to remember our Creator's salvation on the Sabbath helps us understand that worship and Christian instruction are to be a particular focus of the Lord's Day. We should have the Word of God on our hearts and minds at all times, but the Lord's Day is a particularly appropriate day on which to pause and meditate on God, learn from His Word, and remember anew the glories of His salvation (Deut. 6:6–9; Mark 14:22–25).
Coram Deo
In one sense, all of life is worship (1 Cor. 10:31). At the same time, however, it is fitting that we set aside time to gather with God’s people to remember His salvation and to thank Him for His deliverance. The best time to do this is on the day of the week Jesus was raised for our justification, which was the first day of the week that we now commemorate as the Lord’s Day. We should make every attempt to be in church every Sunday.