By virtue of his prayer, and in the name of our Lord Jesus Christ, he healed several persons suffering under various diseases; and he alone, by the assistance of God, expelled from this our island, which now has the primacy, innumerable hosts of malignant spirits, whom he saw with his bodily eyes assailing himself, and beginning to bring deadly distempers on his monastic brotherhood. Partly by mortification, and partly by a bold resistance, he subdued, with the help of Christ, the furious rage of wild beasts. The surging waves, also, at times rolling mountains high in a great tempest, became quickly at his prayer quiet and smooth, and his ship, in which he then happened to be, reached the desired haven in a perfect calm.
When returning from the country of the Picts, where he had been for some days, he hoisted his sail when the breeze was against him to confound the Druids, and made as rapid a voyage as if the wind had been favourable. On other occasions, also, contrary winds were at his prayers changed into fair. In that same country, he took a white stone from the river, and blessed it for the working of certain cures, and that stone, contrary to nature, floated like an apple when placed in water. This divine miracle was wrought in the presence of King Brude and his household. In the same country, also, he performed a still greater miracle, by raising to life the dead child of an humble believer, and restoring him in life and vigour to his father and mother. At another time, while the blessed man was yet a young deacon in Hibernia, residing with the holy bishop Findbarr, the wine required for the Sacred Mysteries failed, and he changed by his prayer pure water into true wine. An immense blaze of heavenly light was on many and wholly distinct occasions seen by some of the brethren to surround him in the light of day, as well as in the darkness of the night. He was also favoured with the sweet and most delightful society of bright hosts of the holy angels. He often saw, by the revelation of the Holy Ghost, the souls of some just men carried by angels to the highest heavens. And the reprobates too he very frequently beheld carried to hell by demons. He very often foretold the future deserts, sometimes joyful, and sometimes sad, of many persons while they were still living in mortal flesh. In the dreadful crash of wars he obtained from God, by the virtue of prayer, that some kings should be conquered, and others come off victorious. And such a grace as this he enjoyed, not only while alive in this world, but even after his departure from the flesh, as God, from whom all the saints derive their honour, has made him still a victorious and most valiant champion in battle.
— St. Adomnán’s Vita Columbæ, Book I, Chapter i.