The heart of Christian worship is the act of asking for forgiveness of sin because the shed blood of Jesus alone washes it away, and because the spotless righteousness of Christ covers our unrighteousness. This conviction of sin arises from a reading of God’s law with opportunity given for all those present to confess their sins, before hearing a biblical word of pardon and assurance. This should tied to the present intercessory work of Jesus Christ, who is at the right hand of the Father interceding for his people, making a defense for his own before the Father (1 John 1:7-2:2).
For the Reformers, Recovering the Gospel Also Meant Recovery of Proper Worship .
The Reformers understood that the recovery of the gospel was directly connected to proper Christian worship. John Calvin, for one, saw his own conversion and subsequent work of reform tied directly to the removal of all forms of Roman idolatry (especially the mass) from Christian worship. The centrality of the gospel to the life of the church must be made manifest in the pure worship of God. This meant a Word-centered liturgy in which biblical texts were preached upon, biblical exhortations and commands were made clear, and biblical promises made to the people of God were to be read for their comfort and assurance. As one writer puts it, “the recovery of the gospel in the Reformation was ultimately a worship war–a war against the idols, a war for the pure worship of God.” Our worship must reflect our gospel, and our gospel must define our worship.
The Reformers Sought to “Reform” the Church’s Worship
While affirming Sola Scriptura and striving to base all liturgical reform on biblical principles of worship, the Reformers carefully considered the practices of the ancient church and the teaching of the church fathers when revising the liturgies they inherited. The goal was to reform the church’s ancient liturgies by striping them of all unbiblical additions, not to compose entirely new liturgies from scratch. “New” and “contemporary” when used in the Reformed tradition in connection to worship, are therefore best understood as “reforming” (i.e., removing all unbiblical accretions, as well as adding those things which are missing), not replacing the ancient liturgies with contemporary fads grounded in popular preferences.
Martin Luther stated that his intention was to not to abolish, but to cleanse the liturgies of “wicked additions” (i.e., Roman inventions) and recover their proper (pious) use. Calvin too sought to remove Roman additions made to the liturgies of the ancient church, which is why his Genevan liturgy (The Form of Ecclesiastical Prayers) was subtitled “According to the Custom of the Ancient Church.” Like Luther, he was no innovator, but a “Reformer.” It was said of Heinrich Bullinger (the Reformed pastor in Zurich and a contemporary of Calvin) that he restored “all things to the first and simplest form of the most ancient, and indeed apostolic tradition.” It is fair to say that “tradition mattered to the Reformers. It was the living faith of the dead, not the dead faith of the living.” 
Returning to the ancient ways meant, in part, incorporating the reading of the Ten Commandments (or “law” texts from throughout the Scriptures), using the Lord’s Prayer (either recited or as a model for prayer), reciting the Apostles’ or Nicene Creeds, God’s people thereby confessing the orthodox faith while effectively uniting the church of the present to the people of God of the past—the so-called “cloud of witnesses” mentioned in Hebrews 12:1.
Reformed Worship Is Catholic but Not Roman
The Reformers took seriously the charge from the church father Cyprian (c. 210-258), “You can no longer have God for your Father, if you do have not the church for your mother.” Calvin expanded on Cyprian’s comment, explaining,
Let us learn even from the simple title `mother’ how useful, indeed how necessary, it is that we should know her. For there is no other way to enter into life unless this mother conceive us in her womb, give us birth, nourish us at her breast, and lastly, unless she keep us under her care and guidance until, putting off mortal flesh, we become like the angels (Matthew 22:30). Our weakness does not allow us to be dismissed from her school until we have been pupils all our lives. Furthermore, away from her bosom one cannot hope for any forgiveness of sins or any salvation, as Isaiah (Isaiah 37:32) and Joel (2:32) testify.
For Calvin, one finds the Word of God proclaimed and the sacraments properly administered in the church. Since word and sacrament are essential to a healthy Christian life, the Christian must seek these things where they can be found. They cannot be found in false churches (i.e., Rome), nor in our age in entrepreneurial churches which are the institutional facade of their charismatic leader, nor in the various so-called “ministries” which mimic the church’s biblical activities but exist apart from all ties to local churches. Those who claim to be Christians, but who have no connection to a local church (or who do not see the importance of joining a local church) need to be reminded that the New Testament knows nothing of a professing Christian who is not a member (or seeking to become one) of a faithful congregation where the proper elements of worship can be found.