St Faustina Kowalska, a Polish nun who died on 5th October 1938 at the age of 33 was Canonised on April 30, 2000 by St John Paul 11 on the occasion of her Canonisation, he declared the 'Feast of Mercy', a feast for the Universal Church.
With the words "Oh what great graces I will grant to souls who recite this Chaplet," Jesus gave St Faustina The Chaplet of Mercy with instruction to make a Novena for nine days, from Good Friday to the following Saturday.
Jesus also asked that the three o'clock, the hour at which He died, we should say the Three O’clock prayer say "At Three O’clock implore My Mercy, especially for sinners ....I will refuse nothing to the soul that makes a request of Me in virtue of My Passion...Run through the whole world and tell of My Mercy."
How to Recite the Chaplet
The Chaplet of Mercy is recited using ordinary rosary beads of five decades. The Chaplet is preceded by two opening prayers from the Diary of Saint Faustina and followed by a closing prayer.
First make the Sign of the Cross.
In the name of the Father, and of the Son, and of the Holy Spirit. Amen.
Then you can pray either, or both, of these two optional opening prayers:
The Three O'Clock Prayer
You expired, Jesus, but the source of life gushed forth for souls, and the ocean of mercy opened up for the whole world. O Fount of Life, unfathomable Divine Mercy, envelop the whole world and empty Yourself out upon us. O Blood and Water, which gushed forth from the Heart of Jesus as a fountain of Mercy for us, I trust in You!
(Repeat three times)
O Blood and Water, which gushed forth from the Heart of Jesus as a fount of mercy for us, I trust in You!
Our Father, Who art in heaven, hallowed be Thy name; Thy kingdom come; Thy will be done on earth as it is in heaven. Give us this day our daily bread; and forgive us our trespasses as we forgive those who trespass against us; and lead us not into temptation, but deliver us from evil, Amen.
Hail Mary, full of grace. The Lord is with thee. Blessed art thou amongst women, and blessed is the fruit of thy womb, Jesus. Holy Mary, Mother of God, pray for us sinners, now and at the hour of our death, Amen.
The Apostles’ Creed
I believe in God, the Father almighty, Creator of heaven and earth, and in Jesus Christ, His only Son, our Lord, who was conceived by the Holy Spirit, born of the Virgin Mary, suffered under Pontius Pilate, was crucified, died and was buried; He descended into hell; on the third day He rose again from the dead; He ascended into heaven, and is seated at the right hand of God the Father almighty; from there He will come to judge the living and the dead. I believe in the Holy Spirit, the holy Catholic Church, the communion of saints, the forgiveness of sins, the resurrection of the body, and life everlasting. Amen.
The Eternal Father
Eternal Father, I offer you the Body and Blood, Soul and Divinity of Your Dearly Beloved Son, Our Lord, Jesus Christ, in atonement for our sins and those of the whole world.
On the 10 Small Beads of Each Decade
For the sake of His sorrowful Passion, have mercy on us and on the whole world.
Repeat for the remaining decades
Saying the "Eternal Father" (6) on the "Our Father" bead and then 10 "For the sake of His sorrowful Passion" (7) on the following "Hail Mary" beads.
Conclude the Divine Mercy Chaplet with Holy God (Repeat three times)
Holy God, Holy Mighty One, Holy Immortal One, have mercy on us and on the whole world.
O Holy and Eternal God, in whom Mercy is endless and the treasury of Compassion inexhaustible, look kindly upon us and increase Your Mercy in us so that in difficult moments, we might not despair nor become despondent, but with increasing confidence, submit ourselves to Your Holy Will, which is Love and Mercy itself. Amen.