Saint Faustina's Diary (Divine Mercy in My Soul), contains at least 14 passages in which Our Lord is quoted as requesting that a "Feast of Mercy" be officially established in the Church.

There is a very close link between the meaning of the Divine Mercy image and the liturgy of the first Sunday after Easter (Divine Mercy Sunday). On that day the Gospel reading throughout the Church is about the appearance of the Risen Christ in the Upper Room, and about the institution of the sacrament of Reconciliation. The rays of blood and water flowing from the Saviour's pierced Heart and the wounds on His hands and feet recall the events of Good Friday.

"I desire that the first Sunday after Easter be the Feast of Mercy." (Diary 299) "I desire that the Feast of Mercy be a refuge and shelter for all souls, and especially for poor sinners. On that day the very depths of My tender mercy are open. I pour out a whole ocean of graces upon those souls who approach the fount of My mercy. The soul that will go to Confession and receive Holy Communion shall obtain complete forgiveness of sins and punishment. On that day all the divine floodgates through which grace flow are opened." (Diary 699) "Souls perish in spite of My bitter Passion. I am giving them the last hope of salvation; that is, the Feast of My Mercy." (Diary 965)

The conditions required to receive such a great grace are: to place complete trust in God, to carry out acts of mercy, to be in a state of grace (having received the sacrament of Confession), and to receive Holy Communion.

The preparation for the Feast is to be a novena consisting of the recitation of the Divine Mercy chaplet for 9 days, beginning on Good Friday. Jesus said, "By this novena, I will grant every possible grace to souls." (Diary 796)

On Sunday, 30th April, 2000, (the canonisation of Saint Faustina and Feast of Divine Mercy), Pope John Paul II announced to the world, "It is important that we accept the whole message that comes to us from the word of God on this Second Sunday of Easter (first Sunday after Easter), which from now on throughout the Church will be called 'Divine Mercy Sunday'."