You can find a short historic review of it's origin here but very quickly, Sr. Faustina was visited by Jesus Himself who revealed that He wanted the world to pray the Chaplet of Mercy and celebrate Divine Mercy Sunday with adoration of a picture of the Divine Mercy (which is shown here). He promised that anyone who prays the novena of the Divine Mercy,which begins on Good Friday and continues for 9 days until the Sunday after Easter, He will grant "every possible grace" to them.
In addition to the above promises for saying the Novena, the Divine Mercy Chaplet (which can be said at any time of year, even daily) has other promises as well:
- It promises a peaceful death when said in the presence of the dying.
- It is also retroactive in a sense as you can pray for persons already diseased who may be in purgatory and the Lord will shower His graces and mercy upon them.
- When praying the Divine Mercy Novena, along with confession and receiving the Eucharist on Divine Mercy Sunday (1st Sunday after Easter) you can receive a plenary indulgence (check out this link for a full explanation of the conditions required to receive the indulgence)!
What is a plenary indulgence you say? Well very basically it's a way, given through the grace of God for you to receive a remission of the punishment of your sins. You can find out more about temporary and plenary indulgences here.
There are other promises as well that I cannot recall at this moment but I highly recommend you read Diary of Saint Maria Faustina Kowalska: Divine Mercy in My Soul which will provide for you a beautiful account of Sr. Faustina's visions and how this novena came about.
Ok so this was just the basics and I hope you will join me this year, starting on Good Friday, in saying the Divine Mercy Novena for the spread of grace, mercy, and peace throughout the world!
Blessings to You and Yours,