The first Sunday after the first full moon after the first day of Spring (reckoned according to the Julian calendar) is the Orthodox Feast of Holy Pascha. Holy Pascha is the Feast of feasts – the defining Feast, the Resurrection of our Lord Jesus Christ from the dead. "And if Christ is not risen, then our preaching is empty and your faith is also empty" (1 Cor. 15:14).
The Orthodox have always called this Feast Pascha (not Easter). "For indeed Christ, our Passover (Gk., Pascha), was sacrificed for us. Therefore let us keep the feast…" (1 Cor. 5:7-8). Pascha is simply the Hebrew word for Passover (Pesach) rendered in Greek, and now English, letters. Not only was our Lord Jesus crucified and raised during the Jewish feast of Passover, but He is the fulfillment of that feast, as He said to His disciples gathered at the table for His Lord's Supper: "With fervent desire I have desired to eat this Passover with you before I suffer; for I say to you, I will no longer eat of it until it is fulfilled in the kingdom of God" (Luke 22:15-16).
Therefore Holy Pascha recalls, contains, and imparts the saving acts of God to His faithful people in the ongoing participation of the Liturgy of Holy Communion in the Church, the Body of Christ of which He is its Head. Christ is the sacrificial Lamb whose blood averts our destruction (cf. Ex. 12:7, 12-13, 46; Jn. 1:29; 19:36); His flesh is our food for the journey out of the bondage of sin to the Promised Land of God's uncreated Kingdom (cf. Ex. 12:8, 11; 13:8-11; Jn. 6:53-57).
Pascha (Passover) led directly to the passage of Israel through the Red Sea where the entire Egyptian army was destroyed in the waters – a precursor to Holy Baptism – and to the Covenant at Mount Sinai with the giving of the Law and Worship of God (cf. Ex. 14-15; 19-25). With the death and resurrection of Christ, the New Covenant is opened to us "in [His] blood" (Matt. 26:28); the High Priest Jesus Christ is the "Liturgist of the sanctuary… He has obtained a more excellent liturgy, inasmuch as He is also Mediator of a better covenant, which was established on better promises" (Heb. 8:2, 6). The faithful rescued from evil now assemble around Christ at His Liturgy to walk in His commandments and commune in His grace and love.
"It is always Pascha" (St. John Chrysostom). Pascha defines Christianity, if indeed it is "Orthodox," that is, giving right glory to God. What we witness during Holy Week and the annual Feast of Pascha in the Church manifests the reality of the Christian life present every day of our existence. "Therefore we were buried with [Christ Jesus] through baptism into death, that just as Christ was raised from the dead by the glory of the Father, even so we also should walk in newness of life" (Rom. 6:4).