Schaff, Philip. History of the Christian Church (The Complete Eight Volumes in One). Amazon Kindle Edition, 2014.
Volume 1, Ch. 9, “Worship in the Apostolic Age.” Loc. 6515-6855
§51 “The Synagogue” (Schaff 2014, Loc. 6520).
Christian worship emerged from the practices of the synagogue. “It was the local centre of the religious and social life of the Jews, as the temple of Jerusalem was the centre of their national life” (Ibid., Loc. 6531). Schaff considers synagogue practice to have begun about the time of Ezra and to have remained more or less consistent since then (Ibid., Loc. 6533). He provides a description of the architecture of a typical synagogue (Ibid., Loc. 6537), as well as the organization (Ibid., Loc. 6549) and the worship (Ibid., Loc. 6554).
§52 “Christian Worship” (Ibid., Loc. 6577).
Schaff observes that early Christian worship was based on the synagogue practices but with the focus on the completed work of Jesus.
§53 “The Several Parts of Worship”(Ibid., Loc. 6598).
Schaff details the elements present in worship meetings: preaching, reading from the Old and New Testament, prayer, singing especially of Psalms, a confession of faith, and the sacraments of baptism and communion. Schaff says of these gatherings, “There is no trace of a uniform and exclusive liturgy; it would be inconsistent with the vitality and liberty of the apostolic churches” (Ibid., oc. 6617). However, he concedes that the basic structure is informed by the Synagogue.
§54 “Baptism” (Ibid., Loc. 6645).
Trinitarian baptism, instituted by Christ, was practiced as a sign of church membership, a replacement of circumcision (Ibid., Loc. 6667). Schaff discusses the administration of baptism for forgiveness and cleansing as well as being a sign of prior conversion. Schaff observes that infant baptism, as circumcision, would be expected (Ibid., Loc. 6706).
§55 “The Lord’s Supper” (Ibid., Loc. 6727).
Schaff holds that the eucharist actively delivers grace to the believer (Ibid., Loc. 6745). In the earliest period he sees it as synonymous with the agape (Ibid., Loc. 6755). This became divisive and disappeared by the third century. Schaff weighs the three basic theories of the institution (Ibid., Loc. 6761), concluding that the explanations should not interfere with unity.
§56 “Sacred Places” (Ibid., Loc. 6772).
Very early there is evidence of Christians assembling together in places set aside for worship.
§57 “Sacred Times - The Lord’s Day” (Ibid., Loc. 6790).
The early Christians, especially of Jewish background, often held to prayer at the third, sixth, and ninth hours. The public worship quickly moved to Sunday, as the day of rest when possible, but especially as the day of resurrection (Ibid., Loc. 6813).