HOLY WEEK, in the Christian ecclesiastical year the week immediately preceding Easter. The earliest allusion to the custom of marking this week as a whole with special observances is to be found in the Apostolical Constitutions (v. 18, 19), dating from the latter half of the 3rd century A.D. Abstinence from wine and flesh is there commanded for all the days, while for the Friday and Saturday an absolute fast is enjoined. Of the particular days of the "great week" the earliest to emerge into special prominence was naturally Good Friday. Next came the Sabbatum Magnum (Holy Saturday or Easter Eve) with its vigil, which in the early church was associated with an expectation that the second advent would occur on an Easter Sunday.
For details of the ceremonial observed in the Roman Catholic Church during this week, reference must be made to the Missal and Breviary. In the Eastern Church the week is marked by similar practices, but with less elaboration and differentiation of rite. See also EASTER, GOOD FRIDAY, MAUNDY THURSDAY, PALM SUNDAY and