Bede's Ecclesiastical History of England, ed. by A.M. Sellar, , at sacred-texts.com
THE same Oswald, as soon as he ascended the throne, being desirous that all the nation under his rule should be endued with the grace of the Christian faith, whereof he had found happy experience in vanquishing the barbarians, sent to the elders of the Scots, among whom himself and his followers, when in banishment, had received the sacrament of Baptism, desiring that they would send him a bishop, by whose instruction and ministry the English nation, which he governed, might learn the privileges and receive the Sacraments of the faith of our Lord. Nor were they slow in granting his request; for they sent him Bishop Aidan, a man of singular gentleness, piety, and moderation; having a zeal of God, but not fully according to knowledge; for he was wont to keep Easter Sunday according to the custom of his country, which we have before so often mentioned,from the fourteenth to the twentieth of the moon; the northern province of the Scots, and all the nation of the Picts, at that time still celebrating Easter after that manner, and believing that in this observance they followed the writings of the holy and praiseworthy Father Anatolius. Whether this be true, every instructed person can easily judge. But the Scots which dwelt in the South of Ireland had long since, by the admonition of the Bishop of the Apostolic see, learned to observe Easter according to the canonical custom.
On the arrival of the bishop, the king appointed him his episcopal see in the island of Lindisfarne,as he desired. Which place, as the tide ebbs and flows, is twice a day enclosed by the waves of the sea like an island; and again, twice, when the beach is left dry, becomes contiguous with the land. The king also humbly and willingly in all things giving ear to his admonitions, industriously applied himself to build up and extend the Church of Christ in his kingdom; wherein, when the bishop, who was not perfectly skilled in the English tongue, preached the Gospel, it was a fair sight to see the king himself interpreting the Word of God to his ealdormen and thegns, for he had thoroughly learned the language of the Scots during his long banishment. From that time many came daily into Britain from the country of the Scots, and with great devotion preached the Word to those provinces of the English, over which King Oswald reigned, and those among them that had received priest’s orders administered the grace of Baptism to the believers.. Churches were built in divers places; the people joyfully flocked together to hear the Word; lands and other property were given of the king’s bounty to found monasteries; English children, as well as their elders, were instructed by their Scottish teachers in study and the observance of monastic discipline. For most of those who came to preach were monks. Bishop Aidan was himself a monk, having been sent out from the island called Hii (Iona)whereof the monastery was for a long time the chief of almost all those of the northern Scots, and all those of the Picts, and had the direction of their people. That island belongs to Britain, being divided from it by a small arm of the sea, but had been long since given by the Picts, who inhabit those parts of Britain, to the Scottish monks, because they had received the faith of Christ through their preaching.