While on his way to Damascus to arrest the Christians there, he was converted by a miraculous apparition of Our Lord. Was it a sudden conversion? It seemed so, and in a sense it was; however, it other ways it was the culmination of his many experiences with Christians, beginning with the martyrdom of St. Stephen. Paul was a young man, given the job of holding the cloaks of those who carried out the sentence of death on St. Stephen. In fact, even when Paul was arresting Christians, he could not help but be impressed by their deep faith, their innocency of life, and their willingness to die for Christ.
Eventually he became the great Apostle of the Gentiles, making three missionary journeys which brought him to the important centers of Asia Minor and southern Europe, making many converts as he travelled. He was beheaded in Rome in 66, and his relics are kept in the Basilica of St. Paul near the Ostian Way.
O God, who, by the preaching of thine apostle St. Paul, hast caused the light of the Gospel to shine throughout the world: Grant, we beseech thee, that we, having his wonderful conversion in remembrance, may show forth our thankfulness unto thee for the same by following the holy doctrine which he taught; through Jesus Christ our Lord, who liveth and reigneth with thee, in the unity of the Holy Spirit, one God, now and for ever. Amen.