Saints were canonized in life. Through prophetic acts (prophecies & miracles) they were said to be and miraculously confirmed to be going to Heaven. Heres are a few cases:
Blessed Virgin Mary
The Blessed Virgin Mary was prophesied to be a Saint and miraculously confirmed to be holy her whole life long in Luke 1:28:
Hail, Full of Grace, the Lord is with you.Luke 1:28
With this, Mary was said by St. Gabriel the Archangel, to be lacking in no grace, including the grace of sanctity & sainthood. From this, we know she would be canonized and was currently the holiest person of Earth, before the conception of Christ.
All generations will call me blessedLuke 1:48
This is a double prophetic confirmation of Mary’s earthly and heavenly sainthood. She, who is lacking in no grace (full of grace), would miss nothing, not even Earthly canonization (see Council of Trent, Session 6, Canon 23).
Indeed, the popes throughout the Ages have taught this as a confirmation of Sainthood.
Mary contributes in a special way to the union of the pilgrim Church on earth with the eschatological and heavenly reality of the Communion of Saints, since she has already been ‘assumed into heaven.’Pope St, John Paul II, Mother of the Redeemer #41.
So we see, from the first to the last, Mary is confirmed as a saint on Earth and later in Heaven, like Christ who came from her as a fruit. She from whom the flesh of Christ came, shared in his glory.
St. John the Baptist
St. John the Baptist, like the Blessed Virgin Mary shared in Christ’s glory from Beginning to End. He lept for joy in the womb of St. Elizabeth.
When an adult Christ said of him:
“Truly, I say to you, among those born of women there has risen no one greater than John the Baptist…”Matthew 11:11
He was confirmed in Sainthood in this verse.
“Having first delivered the Prophet’s testimony in praise of John, He rested not there, but added His own decision respecting him”St. John Chrysostym, Bishop, Church Father, Church Doctor.
So it was, men were canonized amongst the Hebrews before:
When men in the camp were jealous of Moses and Aaron, the holy one (Saint) of the LordPsalm 106:16
Saint Dismas (Thief on the Cross)
St. Dismas, the thief on the Cross, was canonized in life by Christ himself (Luke 23:43). Before his works were complete, he was pronounced a Saint by Jesus.
God knows all things, even the freewill acts of men (Catechism of the Catholic Church, paragraph 208). He knows what a person will do in life, even before they do them. It is through this omniscience that He acts and speaks.
So, with Saint Dismas, he pronounced judgment on even his future acts. The Dogma of the Church confirms this:
If anyone says, that he will for certain, have that great gift of perseverance unto the end, unless have learned this by an absolutely certain and infallible special revelation; let him be anathema.Council of Trent, Session 6, Canon 16.
We also see absolutely certain and infallible special revelations exist today. There is no gift God has withheld from us (Matthew 11:27, John 14:13). It is only our willingness to ask that limits us, within good prudence and the Will of God (Matthew 6:10).
In bilocation, indeed in the future even in my flesh, I hung upon the Cross of St. Dismas for one hour. I did so to accompany my Lord in his suffering. Such pain few experience.
To my right, across from Christ, hung the other thief (who later repented by the power of the Green Scapular), on whose Cross hung the Fiery One of Nations (a Living Saint). We spent an hour with Christ in his greatest moment of suffering.
Through this and many visions, I know Saint Dismas well. A soul of fortitude that refuses to give up on Salvation, even in the last moments of life (Luke 23:40-43).
Saint Dismas, the Saint of Final Repentance. A Saint canonized in life: A Living Saint.