From St. Faustina's Diary:
Eighth DaySay the Chaplet of Divine Mercy.
1226 [Jesus:] Today bring to Me the souls who are in the prison of Purgatory, and immerse them in the abyss of My mercy. Let the torrents of My Blood cool down their scorching flames. All these souls are greatly loved by Me. They are making retribution to My justice. It is in your power to bring them relief. Draw all the indulgences from the treasury of My Church and offer them on their behalf. Oh, if you only knew the torments they suffer, you would continually offer for them the alms of the spirit and pay off their debt to My justice.
1227 [St. Faustina:] Most Merciful Jesus, You Yourself have said that You desire mercy; so I bring into the abode of Your Most Compassionate Heart the souls in Purgatory, souls who are very dear to You, and yet, who must make retribution to Your justice. May the streams of Blood and Water which gushed forth from Your Heart put out the flames of the purifying fire, that in that place, too, the power of Your mercy may be praised.
From the terrible heat of the cleansing fire
Rises a plaint to Your mercy,
And they receive comfort, refreshment, relief
In the stream of mingled Blood and Water.
Eternal Father, turn Your merciful gaze upon the souls suffering in Purgatory, who are enfolded in the Most Compassionate Heart of Jesus. I beg You, by the sorrowful Passion of Jesus Your Son, and by all the bitterness with which His most sacred Soul was flooded, manifest Your mercy to the souls who are under Your just scrutiny. Look upon them in no other way than through the Wounds of Jesus, Your dearly beloved Son; for we firmly believe that there is no limit to Your goodness and compassion.