Jesus dictated the Chaplet of Divine Mercy to Sister Faustina in Vilnius in 1935. In the revelations that followed He disclosed to her its value and efficacy, as well as the promises He attached to it.
Priests, Jesus said, 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. Jesus promised to grant grace to those who recite this prayer at least once in their lifetime, providing it is said with an attitude of complete trust, humility, and a sincere, deep sorrow for sin.
In this prayer we are offering “the Body and Blood, Soul and Divinity” of Jesus Christ to God the Father. We are uniting ourselves with His sacrifice offered on the Cross for the salvation of the world. By offering God the Father His “most dearly beloved Son”, we are using the most convincing argument with which to be heard. We are asking for mercy “for us and for the whole world.” The word “us” refers to the person reciting the chaplet and those for whom he desires to offer it or for whom he should pray. The “whole world” indicates all people living on earth and the souls in Purgatory. By praying the words of this chaplet we are performing an act of love towards our neighbor, which along with trust, is the indispensable condition for obtaining graces.
Jesus promised – It pleases Me to grant everything they ask of Me by saying the chaplet and He added,if (it) … be compatible with My will.