We know that nothing tainted can enter the spiritual realm of purity, the Kindgom of God. At the moment of death, if a person has not reached “perfection,” he cannot enjoy the beatific vision. 

“It has ever been the teaching of the Church . . . that Purgatory exists . . . It is a place or condition wherein the souls of the just undergo that purifying fire that renders them fit for God and the joys of eternal life.”[1]

“All those who die in God’s grace and friendship, but still imperfectly purified, are indeed assured of their eternal salvation; but after death they undergo purification, so as to achieve the holiness necessary to enter the joy of heaven.”[2] 

Throughout his life, he had a special mission through his Masses and prayers to release souls from Purgatory. There are many examples of souls appearing before him asking him to pray for their release.

Padre Pio described one such incident that occurred during World War I at the friary in San Giovanni Rotondo. He had been sitting alone in a guestroom absorbedin prayer one night when an old man entered and sat next to him. 
“I looked at him but never thought of how he had managed to get in the friary at that hours. I asked him: ‘Who are you? What do you want?’ The man answered: ‘Padre Pio, I am Pietro di Mauro, nicknamed Precoco. I died in this friary on September 18, 1908, in room number 4, when this friary was still a home for the elderly. When in bed one night, I fell asleep with my cigar burning. My bed caught fire and I died. I suffocated and burned alive. I am still in Purgatory, and I need a Mass to free my soul from it. God has given me permission to come to you and ask for your prayers.’ After I had listened to his
story I said: ‘You can rest assured that I will celebrate Mass tomorrow for your
liberation.’” Padre Pio related that the Mass he celebrated the next day freed the man’s soul from Purgatory. One of the other priests at the friary later on checked the village records and found that such an individual had indeed died under the circumstances described by Padre Pio.[3] 

[1] Encylopedia of Catholic Doctrine. Ed. Russell Shaw, p. 550f
[2] Catechism of the Catholic Church. #1030-1032
[3] Padre Pio: The Wonder Worker, p. 172. 

Fr. Robert McQueeney, 1919 - 2002
Spiritual Director
The Padre Pio Foundation of America, 1982-2002