In a vision to St. Maria Faustina Kowalska in 1935, the Lord revealed a powerful prayer that He wanted everyone to say -- the Chaplet of The Divine Mercy -- and He promised extraordinary graces to those who would recite it:

 

Whoever will recite it will receive great mercy at the hour of death....Priests will recommend it to sinners as their last hope of salvation.  Even if there were a sinner most hardened, if he were to recite this chaplet only once, he would receive grace from My infinite mercy...I desire to grant unimaginable graces to those souls who trust in My mercy... (Diary, 687)

 

Encourage souls to say the chaplet which I have given you... When they say this chaplet in the presence of the dying, I will stand between My Father and the dying person, not as the just Judge but as the Merciful Savior...(1541)

 

Through the chaplet you will obtain everything, if what you ask for is compatible with My will.  (1731)