Feeling a call to religious life, Smith made his profession as a Benedictine monk of Monte Cassino on 21 March 1847. Because of the Sicilian revolution of 1848, however, he was forced as a British citizen to leave the monastery, which fell within the Kingdom of the Two Sicilies. He was allowed to return to Rome, and from 1850 to 1855 he served as vice-rector of the Irish College. Around this time he was also named professor of dogmatic theology at the Urban College and consultor to the Sacred Congregation of the Index. He was also made consultor to the Oriental Congregation in 1862, to the Holy Office in 1874, and to the Propaganda Fide in 1880.