Do you see, my dear brethren, do you hear that tender mother, that devoted father, and all those relatives who helped and tended you? "My friends," they cry, "free us from these pains; you can do it." Consider then, my dear brethren: (a) the magnitude of these sufferings which the souls in Purgatory endure; and (b) the means which we have of mitigating them: our prayers, our good works, and, above all, the holy sacrifice of the Mass. I do not wish to stop at this stage to prove to you the existence of Purgatory. That would be a waste of time. No one among you has the slightest doubt on that score. The Church, to which Jesus Christ promised the guidance of the Holy Ghost and which, consequently, can neither be mistaken herself nor mislead us, teaches us about Purgatory in a very clear and positive manner. It is certain, very certain, that there is a place where the souls of the just complete the expiation of their sins before being admitted to the glory of Paradise, which is assured them. Yes, my dear brethren, and it is an article of faith: if we have not done penance proportionate to the greatness and enormity of our sins, even though forgiven in the holy tribunal of Penance, we shall be compelled to expiate them.... In Holy Scripture there are many texts which show clearly that although our sins may be forgiven, God still imposes on us the obligation to suffer in this world by temporal hardships or in the next by the flames of Purgatory. Look at what happened to Adam. Because he was repentant after committing his sin, God assured him that He had pardoned him, and yet He condemned him to do penance for nine hundred years, penance which surpasses anything that we can imagine. See again: David ordered, contrary to the wish of God, the census of his subjects, but, stricken with remorse of conscience, he saw his sin and, throwing himself upon the ground, begged the Lord to pardon him. God, touched by his repentance, forgave him indeed. But despite that, He sent Gad to tell David that he would have to choose between three scourges which He had prepared for him as punishment for his iniquity: the plague, war, or famine. David said: "It is better that I should fall into the hands of the Lord (for his mercies are many) than into the hands of men." He chose the pestilence, which lasted three days and killed seventy thousand of his subjects. If the Lord had not stayed the hand of the Angel, which was stretched out over the city, all Jerusalem would have been depopulated! David, seeing so many evils caused by his sin, begged the grace of God to punish him alone and to spare his people, who were innocent. See, too, the penance of Saint Mary Magdalen; perhaps that will soften your hearts a little. Alas, my dear brethren, what, then, will be the number of years which we shall have to suffer in Purgatory, we who have so many sins, we who, under the pretext that we have confessed them, do no penance and shed no tears?St. Jean Marie Baptiste Vianney, Sermon on Purgatory
"We must empty Purgatory." St. Pius of Petraclina, O.F.M.Cap.