In her diary, St. Faustina wrote that Jesus told her:
"On each day of the novena you will bring to My heart a different group of souls and you will immerse them in this ocean of My mercy ... On each day you will beg My Father, on the strength of My passion, for the graces for these souls."
The different souls prayed for on each day of the novena are:
DAY 1 (Good Friday) - All mankind, especially sinners
DAY 2 (Holy Saturday) - The souls of priests and religious
DAY 3 (Easter Sunday) - All devout and faithful souls
DAY 4 (Easter Monday) - Those who do not believe in Jesus and those who do not yet know Him
DAY 5 (Easter Tuesday) - The souls of separated brethren
DAY 6 (Easter Wednesday) - The meek and humble souls and the souls of children
DAY 7 (Easter Thursday) - The souls who especially venerate and glorify Jesus' mercy
DAY 8 (Easter Friday) - The souls who are detained in purgatory;
DAY 9 (Easter Saturday) - The souls who have become lukewarm.
The Chaplet of Divine Mercy may also be offered each day for the day's intention, but is not strictly necessary to the Novena.