Selected quotes from the Diary of Saint Maria Faustina Kowalska
This Feast emerged from the very depth of My mercy and it is confirmed in the vast depth of My tender mercies. Every soul believing and trusting in My mercy will obtain it. (Diary of St. Faustina, entry no. 420)
My 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. 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 graces flow are opened. Let no soul fear to draw near to Me, even though its sins be as scarlet. My mercy is so great that no mind, be it of man or of angel, will be able to fathom it throughout all eternity. Everything that exists has come forth from the very depths of My most tender mercy. Every soul in its relation to Me will contemplate My love and mercy throughout eternity. The Feast of Mercy emerged from My very depths of tenderness. It is My desire that it be solemnly celebrated on the first Sunday after Easter. Mankind will not have peace until it turns to the Fount of My Mercy. (Diary of St. Faustina, Entry No. 699)
The Feast of My mercy has issued forth from My very depths for the consolation of the whole world. (Diary of Saint Faustina, Entry no. 1517)