Saint Paul was born of Jewish parents who were descended from the tribe of
Benjamin. He was a Roman citizen from birth. As he was “a young man” at the
stoning of St. Stephen and calls himself “an old man” when writing to Philemon,
about the year 63, we may conclude that he was born around the beginning of the
Christian era.
To complete his schooling, St. Paul was sent to Jerusalem, and was educated in the
strict observance of the ancestral Law. Here he also acquired a good knowledge of
exegesis and was trained in the practice of disputation. As a convinced and zealous
Pharisee he returned to Tarsus before the public life of Christ opened in Palestine, for
he never refers to personal acquaintance with the Savior during His mortal life.
Sometime after the death of Our Lord, St. Paul returned to Palestine. His profound
conviction and emotional character made his zeal develop into a religious fanaticism
against the infant Church. He took part in the stoning of the first martyr, St. Stephen,
and in the fierce persecution of the Christians that followed.
Entrusted with a formal mission from the high priest, he departed for Damascus to
arrest the Christians there and bring them bound to Jerusalem. As he was nearing
Damascus, about noon, a light from heaven suddenly blazed round him. Jesus with
His glorified body appeared to him and addressed him, turning him away from his
apparently successful career. An immediate transformation was wrought in the soul
of St. Paul. He was suddenly converted to the Christian Faith and arose an Apostle.

NewAvent.com

When we read the Epistles of Saint Paul to the Christians of his time, it is striking
to see with what insistency he speaks of the mystery of Our Lord Jesus Christ. He
constantly returns to this subject which has taken such possession of him that Christ
is his very life: He spends himself, without counting the cost, for Christ and His
members.
Chosen and instructed by Jesus Himself to be the herald of His mystery throughout
the world, he has penetrated so deeply into its depths and glories, that his one desire
is to unveil it and make the adorable Person of Christ known and loved. He writes to
the Colossians that what fills him with joy in the midst of his tribulations is the
thought that it has been given to him to announce “the mystery which hath been
hidden from ages and generations but now is manifested to His saints, to whom God
would make known the riches of the glory of this mystery…which is Christ.: He
refers all his knowledge, all his preaching, all his love, all his life to Jesus Christ. In
the labours and struggles of his apostolate, one of his joys is to think that he is “in
labour” – it is his own expression—until Christ be formed in souls.

Christ the Life of the Soul, pp. 27, 28.