Once we have left this earth, there is nothing we will desire more than the celebration of Holy Mass for our souls. The Holy Sacrifice of the Mass is the most powerful intercessory prayer, for it surpasses every prayer, every penance and every good work. This will not be difficult for us to understand if we recall that the Sacrifice of the Mass is the same Sacrifice of Jesus which He offered on the Cross and which He now offers on all the Alters with its infinite expiatory value. Jesus immolated, is the true Victim of "Propitiation for our sins" (1 John 2:2) and His Divine Blood is effused "unto remission of sins" (Matt. 26:28). Absolutely nothing can be equaled to the Holy Mass, and the saving fruits of the Sacrifice can be extended to an unlimited number of souls. 

One time, during the celebration of the Holy Mass in the Church of St. Paul at the Three Fountains in Rome, St. Bernard saw an unending stairway which went up to Heaven, Very many angels went up and down on it, carrying from Purgatory to Paradise the souls freed by the Sacrifice of the Mass, renewed by priests on the altars all over the world. Therefore, at the death of one of our relatives or friends, let us take much more care how we participate in the Mass for them, rather than the flowers the mourning clothes and the funeral procession....

There are many recounted apparitions of souls being purified in Purgatory who came to ask Padre Pio to offer the Mass for them, so that they would be able to leave Purgatory. One day the Padre offered the Mass for the father of one of his fellow Franciscan Brothers. At the end of the Holy Sacrifice, Padre Pio said to his brother, "This morning the soul of your father has entered into Heaven". The brother was happy to hear this, yet he said to Padre Pio, "But, Father, my good father died thirty-two years ago." "My son," Padre Pio replied, "before God everything has to be paid for." And it is the Holy Mass which obtains for us a price of infinite value: The Body and the Blood of Jesus, the "Immaculate Lamb" (Apoc. 5:12).

We can read in the lives of the Saints how severely even the holiest and most faithful servants of God had to suffer for the smallest sins and imperfections. In the Chronicles of the Friars Minor we read of one of their number who died at Paris, and who on account of his angelic purity and holiness was looked on as more Angel than man. In the same convent there was at the time a very learned theologian, who was also most enlightened in spiritual matters.  He deliberately omitted to say Mass for his deceased brother because he thought it unnecessary to help one who, as he certainly believed, was already high in glory, so great was the fame for sanctity that the deceased had gained during life. But in a few days time the latter appeared to him, and said in a mournful voice: "Dear brother, for God's sake, have pity on me!" The other, terrified, exclaimed: "Holy soul, what do you want from me?" "Masses! Masses!" was the eager answer, "that I may be released from my torments." "What! You in torments? You who have led such an angelic, innocent, and penitential life! Was not that sufficient purification and atonement for you?" "Alas!" sighed the soul, "no one believes how strictly God judges, and how severely He punishes!" And no one does believe how just Almighty God is! How many people are in Purgatory with no one praying for them because they are believed to be in Heaven!

During a sermon one day, the Holy Cure of Ars gave  the example of a priest who, celebrating Mass for his deceased friend, after the Consecration prayed as follows, "Holy and Eternal Father, let us make an exchange. You possess the soul of my friend in Purgatory; I have the Body of Your Son in my hands. You liberate for me my friend, and I offer to You Your Son, with all the merits of His Passion and Death."  

In the life of Blessed Henry Suso we read that as a young man he had made this agreement with a brother of his religious order, "Whichever one of us outlives the other, let him hasten the glory of the one who has passed into eternity with the celebration of one Holy Mass every week." The companion of Blessed Henry died first in a mission territory. Blessed Henry remembered his promise for a little while, then, because he had been obliged to celebrate Masses for others, he substituted the weekly Mass which he had promised his friend with prayers and penances. But his friend appeared to him and scolded him, "Your prayers and your penances are not sufficient for me, I need the Blood of Jesus," "because it is with the Blood of Jesus that we pay the debts of our sins"
(Col. 1:14).  Let us remember that all prayers and good works offered for a soul are good and commendable, but when we can, let us above all have celebrated Holy Masses for the one's who have died.

Also, the great St. Jerome has written that "for every Mass devoutly celebrated many souls leave Purgatory and fly to Heaven." The same must be said for Holy Masses devoutly heard. Let us therefore pray for the souls in Purgatory and free them from their pains by having celebrated and participating in many Holy Masses. "All good works taken together," said the holy Cure of Ars, "cannot have the value of one Holy Mass, because they are the works of men, whereas the Holy Mass is the work of God!"

Source: Jesus our Eucharistic Love.