What are the essential parts of public worship as a perpetual and standing ordinance of God in the church?
Let the confession of faith, and the proposition it lays down in regard to religious worship, furnish an answer to that question. ‘Prayer with Thanksgiving,’ says the Westminster Confession, ‘being one special part of religious worship, is by God required of all men.’ And again: ‘The reading of the Scriptures with godly fear; the sound preaching and conscionable hearing of the Word in obedience, onto God, with understanding, faith, and reverence; singing of Psalms, with grace in the heart; as also the due administration and worthy the receiving of the Sacraments instituted by Christ, are all parts of the ordinary religious worship of God. These four things, then — prayer, the reading and preaching of the Word, singing of psalms, and the dispensation of sacraments – make up the ordinary public worship of God, as designed to be a standing ordinance in the Church, and to be kept up uninterruptedly from one generation to another. All of these are revealed institutions appointed by God in His Word; and some of them are also duties of natural religion.
The Church of Christ – James Bannerman – Public Worship pg. 344