In September 1728 he abandoned the bar and decided to become a priest after commencing his ecclesial studies; Cardinal Francesco Pignatelli incardinated him as a cleric to the parish of Santa Anna di Palazzo. His zeal showed itself at once in his labours for children whom he catechized with wonderful success. On 4 June 1729 he became a boarder at the Collegio della Santa Famiglia to continue his studies under more peaceful conditions though left on 8 April 1730 to enter the novitiate of the Congregation of the Apostolic Missions. He concluded this probation on 28 May 1731. He was ordained to the priesthood on 8 June 1732 and became a member of the Propaganda of Naples which was a congregation of secular priests devoted to apostolic work. He distributed his wealth to the poor. Cardinal Pignatelli assigned him to serve as the Director of Religious Instruction in the parish of Saints Francis and Matthew in the Spanish quarter. He also visited the old people in the Hospice of Saint Gennaro and those condemned to death who were ill in the hospital at the docks. It was at this time that he developed a friendship with Alphonsus Maria de' Liguori after the two first met in Chiaiano.