Bede's Ecclesiastical History of England, ed. by A.M. Sellar, , at sacred-texts.com
FROM this island, then, and the fraternity of these monks, Aidan was sent to instruct the English nation in Christ, having received the dignity of a bishop. At that time Segeni,abbot and priest, presided over that monastery. Among other lessons in holy living, Aidan left the clergy a most salutary example of abstinence and continence; it was the highest commendation of his doctrine with all men, that he taught nothing that he did not practice in his life among his brethren; for he neither sought nor loved anything of this world, but delighted in distributing immediately among the poor whom he met whatsoever was given him by the kings or rich men of the world. He was wont to traverse both town and country on foot, never on horseback, unless compelled by some urgent necessity; to the end that, as he went, he might turn aside to any whomsoever he saw, whether rich or poor, and call upon them, if infidels, to receive the mystery of the faith, or, if they were believers, strengthen them in the faith, and stir them up by words and actions to giving of alms and the performance of good works.
His course of life was so different from the slothfulness of our times, that all those who bore him company, whether they were tonsured or laymen, had to study either reading the Scriptures, or learning psalms. This was the daily employment of himself and all that were with him, wheresoever they went; and if it happened, which was but seldom, that he was invited to the king’s table, he went with one or two clerks, and having taken a little food, made haste to be gone, either to read with his brethren or to pray. At that time, many religious men and women, led by his example, adopted the custom of prolonging their fast on Wednesdays and Fridays, till the ninth hour, throughout the year, except during the fifty days after Easter. Never, through fear or respect of persons, did he keep silence with regard to the sins of the rich; but was wont to correct them with a severe rebuke. He never gave money to the powerful men of the world, but only food, if he happened to entertain them; and, on the contrary, whatsoever gifts of money he received from the rich, he either distributed, as has been said, for the use of the poor, or bestowed in ransoming such as had been wrongfully sold for slaves. Moreover, he afterwards made many of those he had ransomed his disciples, and after having taught and instructed them, advanced them to priest’s orders.
It is said, that when King Oswald had asked a bishop of the Scots to administer the Word of faith to him and his nation, there was first sent to him another man of more harsh disposition,who, after preaching for some time to the English and meeting with no success, not being gladly heard by the people, returned home, and in an assembly of the elders reported, that he had not been able to do any good by his teaching to the nation to whom he had been sent, because they were intractable men, and of a stubborn and barbarous disposition. They then, it is said, held a council and seriously debated what was to be done, being desirous that the nation should obtain the, salvation it demanded, but grieving that they had not received the preacher sent to them. Then said Aidan, who was also present in the council, to the priest in question, "Methinks, brother, that you were more severe to your unlearned hearers than you ought to have been, and did not at first, conformably to the Apostolic rule, give them the milk of more easy doctrine, till, being by degrees nourished with the Word of God, they should be capable of receiving that which is more perfect and of performing the higher precepts of God." Having heard these words, all present turned their attention to him and began diligently to weigh what he had said, and they decided that he was worthy to be made a bishop, and that he was the man who ought to be sent to instruct the unbelieving and unlearned; since he was found to be endued preeminently with the grace of discretion, which is the mother of the virtues. So they ordained him and sent him forth to preach; and, as time went on, his other virtues became apparent, as well as that temperate discretion which had marked him at first.