The Most Ancient Lives of Saint Patrick/The Life and Acts of St. Patrick/Chapter 87
How the Tooth of Saint Patrick shone in the River.
And on a time the saint, with his holy company, passed over a certain river named Dabhall; and for that the day declined and the evening came on, he prepared to pass the night near the bank, and pitched his tent on a fair plain. And approaching the water, he washed his hands and his mouth, and with his most pious fingers he rubbed his gums and his teeth; but through age or infirmity one of his teeth, by chance, or rather by the divine will, dropped out of his mouth into the water; and his disciples sought it diligently in the stream, yet with all their long and careful search found they it not. But in the darkness of the night the tooth lying in the river shone as a radiant star, and the brightness thereof attracted all who dwelled near to behold and to admire. And the tooth so miraculously discovered is brought unto the saint, and he and all around him offer thanks to the Almighty, who had brought this thing to pass; and on that spot he builded a church, and deposited the tooth beneath the altar. The which is famed for divers miracles, and even to this day is called Cluayn Fiacal—that is, the Church of the Tooth. And the tooth of Saint Patrick, like a radiant star, shone by the same divine grace whereby, at the prayer of Samson, the conqueror of the Philistines, a fountain of water streamed forth from the jaw-bone of an ass. And this church is distant about five miles from the metropolitan city of Ardmachia.