This holy pope succeeded St. Alexander about the end of the reign of Trajan, and governed the church ten years, at a time when that dignity was the common step to martyrdom; and in all martyrologies he is honored with the title of martyr. But it seems to be Sixtus II. who is mentioned in the canon of the mass, whose martyrdom was more famous in the church. A portion of the relics of St. Sixtus I., given by pope Clement X. to cardinal de Retz, was by him placed with great solemnity in the abbey of St. Michael in Lorraine.
Those primitive pastors who were chosen by God to be his great instruments in propagating his holy faith, were men eminently endued with the spirit of the most heroic Christian charity, so that we wonder not so much that their words and example were so powerful in converting the world, as that any could be so obstinate as to resist the spirit with which they delivered the divine oracles, and the miracles and sanctity of their lives, with which they confirmed their mission.
(Adapted from Butler’s Lives of the Saints )