From St. Finnbarr's school Cummian seems to have gone to visit his half brother Guaire, who was King of South Connaught at this period, or a little later on. As Cummian was already famous for sanctity and learning, and belonged to an influential family, who would now be ready enough to acknowledge the relationship, we can easily conceive how his own merits and Guaire's influence, would have procured his selection for the bishopric of Clonfert. "All the Martyrologies and Annals," says Cardinal Moran,[193] "agree in styling St. Cummian Fada, Bishop and Abbot of Clonfert." But it is not easy to fix the exact date of his appointment. We find the death of Senach Garbh, Abbot of Clonfert, marked by the Four Masters under the date of A.D. 620, and his successor Colman died, according to Archdall, in the same year which he gives as A.D. 621. As there is no other obituary of a Bishop or Abbot of Clonfert noticed in our Annals until the death of Cummian himself in A.D. 661, we may, perhaps, fairly assume that he succeeded the Abbot Colman and governed the See for forty years. Colman, King of Connaught, the uncle of Cummian and father of Guaire, was slain in A.D. 617, and Guaire, if not actually king at this date, was an influential chief, and his defeat with others at the battle of Carn Fearadhaigh in Limerick is noted by the annalists in A.D. 622, and his death in A.D. 662, so that the two brothers, the Bishop and Chieftain, were contemporaries ruling in South Connaught during a long and chequered career. This fact will help to explain the great influence which Cummian possessed, and the leading position which he occupied in the Irish Church at that period.[194] His fame as a saint and scholar spread throughout all Ireland, and attracted crowds of students to his great school at Clonfert. He appears, as we shall see further on, to have taken a leading part in the Synod of Magh Lene, held about A.D. 630, and no doubt it was at the request of the Fathers of that Synod, that he wrote his famous epistle on the Paschal Question to the Abbot Segienus of Hy, about the year A.D. 634. There is every reason to believe that Segienus and Cummian were, if not personal friends, at least well known to each other, for the Columbian Abbey of Durrow in King's County, was not far from Clonfert, and the uncle of Segienus had been Abbot of that house until he was transferred to Hy in the year A.D. 600. Segienus himself was very likely educated there under his uncle's care, and perhaps succeeded him later on in the government of the Abbey. It is at all events certain that frequent intercourse existed between Hy and Durrow; and that Cummian must have been well known at Durrow is manifest.