The Most Ancient Lives of Saint Patrick/The Life and Acts of St. Patrick/Chapter 90
The River is Divided in Twain, and Blessed.
On a certain time Saint Patrick came unto a deep and impassable river named Boallus; and as neither boat nor vessel was at hand, he prayed and divided the river in twain, and made unto himself and his followers a free passage. And raising his right hand, he blessed the river, and even to this day the eastern part of the stream can be passed by horsemen and by footmen; yet over the western part cannot any pass unless in some vessel. And being so blessed, this river abounded in fishes beyond all others. Then to his disciples marvelling, and seeking to know the cause of this so great miracle, did the saint answer: "The yet unborn son of life, who will be named Columba, after the lapse of many years will live in this place, and the water thus divided will, for several purposes, be needful unto him and his fellow-militants in Christ, while its abundance of fishes will minister food unto his brethren." And Saint Columba being after many years born, when he became a man builded there a stately monastery, and by his dwelling and by his works approved the prophecy of Patrick.