He was a native of Rome. Because of his virtue and love for all, the faithful made him Pope against his will upon the death of Pope Miltiades in 314. He was Pope when Constantine the Great ended the persecution of the Church, and personally instructed the Emperor in the Faith. Unable to attend the Council of Nicaea personally, he sent delegates to represent him and uphold the Orthodox faith there. He reposed in peace in 325.
Once, in a debate between the Saint and Zambrius, a Jewish scribe and occultist, Zambrius whispered a magic word in the ear of a bull, upon which the animal fell down dead. Zambrius then challenged the Pope to do as much in the name of Christ. The holy bishop replied, ‘My God gives life and resurrection, not death.’ Lifting his hands to heaven, he restored the creature to life. The Emperor and the crowd who witnessed the debate cheered the Saint, and many decided to be baptized.