We perform divine service publicly according to the sanctification of the Sabbath as follows: by teaching, listening, administering the sacraments, assembling together. On these days, we forbid work that hinders the public sanctification of the Sabbath, As did Christ and the apostles. We keep the “eighth day” or the first day of the week as the Lord’s Day. We do not forget works in the service of charity, the necessity of one’s neighbor, and of mercy; for these works are the greater part of divine worship. God is more greatly honored by these in the church of Christ than by arbitrary ceremonies. Christians are lords of the Sabbath; therefore, we choose those days that we wish for public sanctification. As days, per se, are equal, so we do not elevate one day above another, except with respect to the ministry of the church and public sanctification. We do not superstitiously proclaim feasts in the manner of the papists. We observe the festivals of Christ’s birth, circumcision, passion, Easter, and Pentecost for certain reasons, without superstition. We have rejected from our church, on account of various superstitions and idolatry, the fictitious festivals of saints, martyrs, the blessed virgin and other virgins. The Sabbath must be made sacred to the Lord alone, not to created things, etc..(Ex. 20, 34; Deut. 4, 5). The day must be made sacred to God, not dead men. As it is written:”sanctify the Sabbath Day”(Ex. 20:8). To sanctify the sabbath is to worship God. Therefore it must be sanctified to God alone, as he alone is to be worshiped. We often recite in public the histories of the saints since we often refer to and expound their writings in our sermons. Therefore, as it is contrary to the command of God to make the Sabbath sacred to the saints, we do not do that; and those who ordain and dedicate festivals to them, we repudiate (Augustine condemns idolatrous human feasts also, Book 18, 10).
—The Hungarian Confessio Catholica (1562) in Reformed Confessions of the 16th and 17th Centuries in English Translation, ed. James T. Dennison, Jr., 4 vol. (Grand Rapids: Reformation Heritage Books), 2.606–07.