Schaff, Philip. History of the Christian Church (The Complete Eight Volumes in One). Amazon Kindle Edition, 2014.
Volume 2, Ante-Nicene Christianity A.D. 100-325, “Chapter 5. Christian Worship” (Includes an introduction and sections 59-74).
§60. The Lord’s Day.
Schaff ties celebration of the Lord’s day directly to the apostolic period. “Nothing short of apostolic precedent can account for the universal religious observance in the churches of the second century. There is no dissenting voice” (Schaff 2014, Loc. 14815). Although no secular culture observed a day off, Christianity was uniform in arranging for gatherings on the first day of the week. Schaff notes that Christians did not consider the Lord’s Day as a Sabbath, but as a replacement of the Sabbath (Schaff 2014, Loc. 14822). It was not a day of rest but a day to celebrate the resurrection. Legislation pertaining to Sundays was unknown prior to Constantine. However, many Christians had habits of avoiding fasts on Sunday. They also would stand to pray on that day, signifying the relationship of a child of the King, rather than that of a servant. (Schaff 2014, Loc. 14855).