Sunday.
The first day of the week, kept because that is the day the tomb was found empty. Everything else in the practice hangs off it — the calendar, the working week of most of the planet, and the one hour a large minority of humanity still gives to something it cannot prove.
Sunday is the oldest Christian institution — earlier than the canon, earlier than the creeds, earlier than any church building. The second-century letter of Pliny to Trajan already describes Christians meeting before dawn on a fixed day, singing to Christ as to a god, and binding themselves by oath not to steal or commit adultery. The choice of the first day rather than the seventh marked the group off from the synagogue almost immediately. What happens in the hour has varied enormously — the Ethiopian rite and a Kansas megachurch share almost no surface features — but the frame has not: words read, words preached, prayers made, a meal. When Christians describe losing their faith, the thing they most often describe stopping is this.
They were in the habit of meeting on a fixed day before it was light, when they sang in alternate verses a hymn to Christ, as to a god, and bound themselves by a solemn oath, not to any wicked deeds, but never to commit any fraud, theft or adultery.
Pliny the Younger, Letters 10.96, to the Emperor Trajan, c. 112 CE (Melmoth translation)A Roman governor describing the practice from outside — the earliest non-Christian account of a Sunday gathering.
The same ground, other faiths
rites that share this one's ideasSign in to open the first thread. Everything here is attributed.