Jesus is demonstrating to Saint Faustina that our special prayers to Divine Mercy are not just for the person that offers them, but are primarily intercession prayers through which He grants countless souls graces and mercy through these holy prayers.
“If you say this prayer, with a contrite heart and with faith, on behalf of some sinner I will give that soul the grace of conversion”.
"O Blood and water that gushed forth from the heart of Jesus, as a fount of mercy for us, I trust in You”.
Jesus is demonstrating to Saint Faustina that our special prayers to Divine Mercy are not just for the person that offers them, but are primarily intercession prayers through which He grants countless souls graces and mercy through these holy prayers. The Chaplet of Divine Mercy is especially an atonement prayer. Atoning not for my sins but for our sins, which means for our family lineage, i.e. all those in our family ancestry who have gone before us and all those in our family lineage that have yet to be born, which of course covers you and your immediate family as well.
This prayer goes on then to seek mercy for the whole world, which is why it is such a powerful intercession prayer. And remember by reciting this prayer you are answering His call of “Will You Help Me?” and you are reciting words that came from Jesus’ lips because these words were dictated by Jesus to Saint Faustina to be a powerful intercession tool on earth, in her mission to help Him save sinners through His Divine Mercy.
The other powerful prayer He gave her was the conversion prayer, given for sinners who had lost their faith, in this prayer also dictated to Saint Faustina directly by Jesus, He promises to come into the life of any person that this prayer is said for, providing it is said with a contrite heart and with faith in His Divine Mercy. This prayer has become more known as the “Three O’clock Prayer” rather than the more accurate title, “Prayer for the Conversion of Sinners”.
The following passage for St. Faustina’s Diary relate to this new prayer:
Today Jesus said to me, I desire that you know more profoundly the love that burns in My Heart for souls, and you will understand this when you meditate upon My Passion. Call upon My mercy on behalf of sinners; I desire their salvation. When you say this prayer, with a contrite heart and with faith on behalf of some sinner, I will give him the grace of conversion. This is the prayer:“O Blood and Water, which gushed forth from the Heart of Jesus as a fount of Mercy for us, I trust in You.” (Diary 186, 187)
The Lord said to me, The loss of each soul plunges Me into mortal sadness. You always console Me when you pray for sinners. The prayer most pleasing to Me is prayer for the conversion of sinners. Know, My daughter, that this prayer is always heard and answered. (Diary 1397)
By praying this prayer, especially for sinners or those who will die unprepared, you will be participating in the redemption of mankind and saving souls which are very precious to Jesus. Even if we find it difficult to comprehend or believe in the power of this intercessory prayer, we must act with faith and trust that Jesus will honour His promise to save the souls of those for whom this prayer is offered.