Among all of the elements of devotion to The Divine Mercy requested by our Lord through St. Maria Faustina Kowalska, the Feast of Mercy holds first place. The Lord's will with regard to its establishment was already made known in His first revelation to the saint, as recorded in her Diary. In all, there were 14 revelations concerning the desired feast.
Our Lord's explicit desire is that this feast be celebrated on the first Sunday after Easter. This Sunday is designated in "The Liturgy of the Hours and the Celebration of the Eucharist" as the "Octave Day of Easter." It was officially called the Second Sunday of Easter after the liturgical reform of Vatican II. Now, by the Decree of the Congregation for Divine Worship and the Discipline of the Sacraments, the name of this liturgical day has been changed to: "Second Sunday of Easter, or Divine Mercy Sunday."
'Now On Throughout the Church'
Pope John Paul II made the surprise announcement of this change in his homily at the canonization of St. Faustina on April 30, 2000. There, he declared: "It is important then that we accept the whole message that comes to us from the word of God on this Second Sunday of Easter, which from now on throughout the Church, will be called ‘Divine Mercy Sunday.' "
By the words "the whole message," Pope John Paul II was referring to the connection between the "Easter Mystery of the Redemption" — in other words, the suffering, death, burial, resurrection, and ascension of Christ, followed by the sending of the Holy Spirit — and this Feast of Divine Mercy, the Octave Day of Easter, which fulfills the grace of atonement as lived through by Christ Jesus and offered to all who come to Him with trust.
This connection is evident from the scripture readings appointed for this Sunday. As John Paul said, citing the Responsorial Psalm of the Liturgy, "The Church sings … as if receiving from Christ's lips these words of the Psalm." "Give thanks to the Lord for He is good; His steadfast love (= mercy) endures forever" (Ps 118:1). And then, Pope John Paul II developed the connection further: "[This comes] from the lips of the risen Christ, who bears the great message of Divine Mercy and entrusts its ministry to the Apostles in the Upper Room: ‘Peace be with you. As the Father has sent Me, even so I send you. … Receive the Holy Spirit. If you forgive the sins of any, they are forgiven; if you retain the sins of any, they are retained" (Jn 20:21-23).
The Importance of the Image
During his homily, John Paul also made clear that the Image of The Divine Mercy St. Faustina saw, which is to be venerated on Divine Mercy Sunday, represents the Risen Christ bringing mercy to the world (see Diary 49, 88, 299, 341, 570, 742). Pope John Paul II said: "Jesus shows His hands and His side [to the Apostles]. He points, that is, to the wounds of the Passion, especially the wound in His Heart, the source from which flows the great wave of mercy poured out on humanity.
"From that Heart, Sr. Faustina Kowalska, the blessed whom from now on we will call a saint, will see two rays of light shining from that Heart and illuminating the world: ‘The two rays,' Jesus Himself explained to her one day, ‘represent blood and water' (Diary, 299).
"Blood and water! We immediately think of the testimony given by the Evangelist John, who, when a soldier on Calvary pierced Christ's side with his spear, sees blood and water flowing from it (see Jn 19:34). Moreover, if the blood recalls the sacrifice of the cross and the gift of the Eucharist, the water, in Johannine symbolism, represents not only Baptism but also the gift of the Holy Spirit" (see Jn 3:5; 4:14; 7:37-39).
The Meaning of the Day
Clearly, Divine Mercy Sunday is not a new feast established to celebrate St. Faustina's revelations. Indeed, it is not primarily about St. Faustina at all — nor is it altogether a new feast! As many commentators have pointed out, The Second Sunday of Easter was already a solemnity as the Octave Day of Easter; nevertheless, the title "Divine Mercy Sunday" does highlight and amplify the meaning of the day. In this way, it recovers an ancient liturgical tradition, reflected in a teaching attributed to St. Augustine about the Easter Octave, which he called "the days of mercy and pardon," and the Octave Day itself "the compendium of the days of mercy."
Liturgically the Easter Octave has always been centered on the theme of Divine Mercy and forgiveness. Divine Mercy Sunday, therefore, point us to the merciful love of God that lies behind the whole Paschal Mystery — the whole mystery of the death, burial and resurrection of Christ — made present for us in the Eucharist. In this way, it also sums up the whole Easter Octave. As Pope John Paul II pointed out in his Regina Caeli address on Divine Mercy Sunday, 1995: "the whole octave of Easter is like a single day," and the Octave Sunday is meant to be the day of "thanksgiving for the goodness God has shown to man in the whole Easter mystery."
Given the liturgical appropriateness of the title "Divine Mercy Sunday" for the Octave Day of Easter, therefore, the Holy See did not give this title to the Second Sunday of Easter merely as an "option," for those dioceses who happen to like that sort of thing! Rather, the decree issued on May 5, 2000, by the Sacred Congregation for Divine Worship and The Discipline of the Sacraments clearly states: "the Supreme Pontiff John Paul II has graciously determined that in the Roman Missal, after the title Second Sunday of Easter, there shall henceforth be added the appellation ‘or [that is] Divine Mercy Sunday'…".
Divine Mercy Sunday, therefore, is not an optional title for this solemnity; rather, Divine Mercy is the integral name for this Feast Day. In a similar way, the Octave Day of the Nativity of Our Lord was named by the Church "The Feast of the Mother of God."
Not Just an Option
This means that preaching on God's mercy is also not just an option for the clergy on that day — it is soundly expected. To fail to preach on God's mercy on that day would mean largely to ignore the prayers, readings and psalms appointed for that day, as well as the title "Divine Mercy Sunday" now given to that day in the Roman Missal.
Clearly, the celebration of Divine Mercy Sunday does not compete with, nor endanger the integrity of, the Easter Season. After all, Divine Mercy Sunday is the Octave Day of Easter, a day that celebrates the merciful love of God shining through the whole Easter Triduum and the whole Easter mystery. It is a day of declaration of reparation for all sin, thus the Day of Atonement.