The most special grace promised by our Lord for Mercy Sunday is nothing less than the equivalent of a complete renewal of baptismal grace in the soul: โcomplete forgiveness (remission) of sins and punishment.โ Such a measure of grace can only be received otherwise through baptism itself, or through making a sacramental confession as an act of perfect contrition for sin, out of pure love for God.
In her Diary, St. Faustina records a special promise given to her by Jesus. He told her to communicate it to the whole world:
โMy daughter, tell the whole world about My inconceivable mercy. I desire that the Feast of Mercy be a refuge and shelter for all souls, and especially for poor sinners. I pour out a whole ocean of graces upon those souls who approach the fount of My mercy.โ Divine Mercy in My Soul # 699
In three places in her Diary, St. Faustina records our Lordโs promises of specific, extraordinary graces:
โI want to grant a complete pardon to the souls that will go to Confession and receive Holy Communion on the Feast of My mercy.โ Divine Mercy in My Soul # 1109
โWhoever approaches the Fountain of Life on this day will be granted complete forgiveness of sins and punishment.โ Divine Mercy in My Soul # 300
โThe soul that will go to Confession and receive Holy Communion will obtain complete forgiveness of sins and punishment.โ Divine Mercy in My Soul # 699
To receive these graces, the only condition is to receive Holy Communion worthily on Divine Mercy Sunday (or the Vigil celebration) by making a good confession beforehand and staying in the state of grace and trusting in His Divine Mercy.
By these conditions, our Lord is emphasizing the value of confession and Holy Communion as miracles of mercy. The Eucharist is Jesus, Himself, the Living God, longing to pour Himself as Mercy into our hearts.
In addition, our Lord says through St. Faustina that we are to perform acts of mercy:
โYes, the first Sunday after Easter is the Feast of Mercy, but there must also be acts of mercyโ Divine Mercy in My Soul # 742
โThe graces of My mercy are drawn by means of one vessel only, and that is trust. The more a soul trusts, the more it will receiveโ Divine Mercy in My Soul # 1578
The worthy reception of the Eucharist on Divine Mercy Sunday is sufficient to obtain the extraordinary graces promised by Jesus.