CCC 1169 Therefore Easter is not simply one feast among others, but the “Feast of feasts,” the “Solemnity of solemnities,” just as the Eucharist is the “Sacrament of sacraments” (the Great Sacrament). St. Athanasius calls Easter “the Great Sunday”1 and the Eastern Churches call Holy Week “the Great Week.” The mystery of the Resurrection, in which Christ crushed death, permeates with its powerful energy our old time, until all is subjected to him.
1 St. Athanasius (ad 329) ep. fest. 1: PG 24, 1366.