On the Catholic Priesthood
Seventeeth Day: The Manner in which the Church bestows Indulgences upon the Souls in Purgatory
The Church does not apply indulgences to the souls in Purgatory as she does to the faithful upon earth through the tribunal of penance and absolution, but confers them simply through pious supplications and sacrifices offered in their behalf; thus they are relieved indirectly. Holy Church opens her rich treasures of merit and satisfaction in proportion to the suffrage of the faithful, who offer expiation and fervent prayers to God for the relief of the suffering souls.
God has reserved to Himself the right to accept entirely, or in part, the satisfaction offered for any soul in Purgatory. This acceptance depends upon His holy and adorable Will, and perhaps, in great measure upon the care of the soul to render herself worthy of the Divine Assistance during her earthly career. Besides, there may be some obligation neglected by the person who intends to gain the indulgence, owing to ignorance or forgetfulness on his part.
Therefore, we have no assurance whatever that an indulgence given by us to the souls has had the desired effect. Considering this, we should prepare most carefully, and fulfill all obligations required for gaining an indulgence. However, let us place with entire confidence in the tender hand of Divine Mercy the application of indulgences to departed souls who are especially dear to us.
Prayer: Have mercy, O Lord, upon the suffering souls in Purgatory; mitigate the severity of Thy judgments; let the infinite merits of Thine only begotten Son and those of Thy saints assist the holy souls and deliver them from their sufferings. Through Christ Our Lord. Amen.
Prayer for Priests in Purgatory: My Jesus, by the sorrows Thou didst suffer in Thine Agony in the Garden, in Thy Scourging and Crowning with thorns, in the Way to Calvary, in Thy Crucifixion and Death, have mercy on the souls of priests in Purgatory, especially those most forgotten and who have no one else to pray for them. I wish to remember all those priests who ministered to me, the priests my heart has never forgotten, and for those that I no longer recall due to my frailty of memory. Do Thou deliver them from the dire torments they endure; call them and admit them to Thy most sweet embrace in Paradise.
Pope Saint Pius X and Saint John Vianney, pray for us and especially for our priests. Amen
Special Intercession: Pray for the souls of those who neglected to gain indulgences for the souls in Purgatory.
Lord grant them eternal rest, and let perpetual light shine upon them. May they rest in peace. Amen. (three times)
Invocation: My Jesus, mercy!
Source: Manual of the Purgatorian Society, Redemptorist Fathers. 1907
Resource on Indulgences: