Notably, Bucer shows relative indifference to which passage serves the Law-function, as he does likewise with texts used for pardon: “Sometimes [the minister] takes other Words which comfort us in the forgiveness of sins and in the ransom of Christ for our sins, such as St. John 3:16, or 3:35-6, or Acts 10:43, or John 2:1-2.” Flexibility is apparent in Calvin’s approach as well, though he preferred greater regularity. Deddens observes that, while Calvin served in Strasbourg—where he enjoyed considerably more liturgical freedom than in Geneva—his service began as follows:
- Invocation (Psa 121:2, “My help comes from the Lord, who made heaven and earth.”)
- Confession of sins
- Words of pardon and comfort, with Scriptural absolution (i.e., 1 Tim 1:15-17) 
- Ten Commandments
Calvin placed the Decalogue after confession and pardon to emphasize that full-orbed obedience is the covenantal response appropriate for Christians, and not the meritorious ground of our forgiveness.  Moreover, Calvin did not simply recite the Commandments; rather, the congregation sang a rhyming version he wrote for that purpose. Each command was followed by the phrase, “Lord, have mercy upon me.”  Moreover, he punctuated the first and second “tables” of the Law with a brief prayer.
Upon returning to Geneva, Calvin was prevented from using his musical version in the service, but continued reciting the Ten Commandments each Lord’s Day morning. We see that his incorporation of the Decalogue was driven by certain principles (to guide our response to forgiveness) yet reflects considerable freedom (sung/spoken; dividing the tables, etc). Moreover, there is no indication he felt their absence would be sub-Christian. Calvin regarded the presence and placement of confession, absolution, and moral guidance prior to the sermon as more important than the texts chosen to incite them.
The Use of the Decalogue in the Netherlands and Canada
Following the Reformation, the use of Ten Commandments underwent several changes in the Netherlands. Petrus Dathenus’ liturgical guidebook (1562) reflects a growing trend to place the Decalogue before confession of sin, rather than after pardon as Calvin had done, arguably shifting its significance primarily to guilt rather than gratitude.  The first synod in the Netherlands, held in Dordrecht in 1574, removed confession of sins and absolution as necessary elements in worship, yet retained the sung-version of the Ten Commandments, suggesting a loss of understanding about the intended purpose. 
In 1923, the Synod of Utrecht was urged to reintroduce the confession and declaration of forgiveness into the formula of worship, but chose not to. Finally, Synod of Kampen 1975 revisited the issue and adopted much of Calvin’s liturgical formula. “The Synod of the Canadian Reformed Churches at Cloverdale 1983 followed the sister churches in the Netherlands by recommending to the churches this second order of liturgy.” 
CRC and URCNA Use of the Ten Commandments
The 1923 and 1930 Acts of the Christian Reformed Church include reading of the Law as part of weekly services. As well, the Christian Reformed Service Book (1981) includes responsive readings of the Law (not exclusively the Decalogue). The use of the Ten Commandments is less defined in the URCNA. The Church Order (6th Ed.) states that confession of sins is to be made each Lord’s Day, but does not specify which texts, if any, are to be used for this purpose. Furthermore, I searched the minutes of the previous eight synods (1996-2012) and found no references to either the Decalogue/Ten Commandments as a fixed element in the order of service.
The value of the Ten Commandments to elicit confession of sins and guide Christian obedience has lead many Reformed churches to incorporate sung or spoken versions into weekly liturgies. There is no indication from Scripture, however, that the Decalogue alone serves that purpose. Which texts are used is a matter of wisdom, not rule. Moreover, notable figures such Bucer and Calvin expressed flexibility in the frequency and position which the Decalogue had in worship. The most important factor, I believe, is to understand and communicate the principles behind inclusion of the Law in the service, lest it become a dead ritual. Its position prior the sermon is arguably more vital than which text is chosen to illustrate guilt and gratitude. Nonetheless, the Ten Commandments cover the full gamut of covenantal godliness in a way that few, if any, other texts do. Regular, if not weekly, recitation of the Ten Commandments solidifies a sense of the full-orbed obedience which God’s righteousness requires, that is imputed through faith in Christ alone, and is being realized by the Spirit who sanctifies us to keep not some, but all of the Law.
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