The Most Ancient Lives of Saint Patrick/The Life and Acts of St. Patrick/Chapter 178
The Soul of a Certain Sinner is by Saint Patrick freed from Demons.
And on a time a certain saint, named Kaennechus, saw in Hibernia troops of demons passing along, armed with infernal instruments; whom having adjured in the name of the Holy Trinity, he compelled to declare the cause of their coming thither. And they, thus adjured, confessed, though unwillingly, that they came to bear away the soul of a certain most wicked sinner, who for his sins deserved to be carried into hell. Then Kaennechus enjoined them in the name of the Lord to return unto him, and to tell him what they had done. And after some hours had passed, the demons returned with confusion, and declared that by the power of Patrick they had lost their expected prey; for that this man had in every year during his life celebrated with a great feast the festival of Saint Patrick, and had every day repeated certain chapters of the hymn which had been composed in his honor; and therefore, they said, had Saint Patrick snatched him from their hands, as his own proper right. Thus saying, the demons vanished into thin air; and Kaennechus rejoiced in these things, and by the relation excited many unto the frequent repetition of this hymn in honor of Saint Patrick.