Schaff, Philip. "The Lord's Day and the Christian Week." The Oldest Church Manual Called the Teaching of the Twelve Apostles. Second Edition, Revised and Enlarged. New York: Funk & Wagnalls, 1886, 27-28.
The Lord's Day is the day of assembly identified in the Didache (Schaff 1886, 27). At this time, the congregation assembles, making sure they have resolved all conflicts. The eucharist is celebrated, and is considered a pure sacrifice before God. Schaff observes that we can assume the congregation participated in readings from the Old Testament, as this was a long standing habit, recorded in early authors. The first day of the week was also important in other sources, though Schaff also finds Wednesday and Friday as important days for fasting (Schaff 1886, 28). They were also recognized as the days of betrayal and of the death of Christ.