Bede's Ecclesiastical History of England, ed. by A.M. Sellar, , at sacred-texts.com
OSWALD, the most Christian king of the Northumbrians, reigned nine years, including that year which was held accursed for the barbarous cruelty of the king of the Britons and the reckless apostacy of the English kings; for, as was said above,it is agreed by the unanimous consent of all, that the names and memory of the apostates should be erased from the catalogue of the Christian kings, and no year assigned to their reign. After which period, Oswald was killed in a great battle, by the same pagan nation and pagan king of the Mercians, who had slain his predecessor Edwin, at a place called in the English tongue Maserfelth, in the thirty-eighth year of his age, on the fifth day of the month of August.
How great his faith was towards God, and how remarkable his devotion, has been made evident by miracles even after his death; for, in the place where he was killed by the pagans, fighting for his country, sick men and cattle are frequently healed to this day. Whence it came to pass that many took up the very dust of the place where his body fell, and putting it into water, brought much relief with it to their friends who were sick. This custom came so much into use, that the earth being carried away by degrees, a hole was made as deep as the height of a man. Nor is it surprising that the sick should be healed in the place where he died; for, whilst he lived, he never ceased to provide for the poor and the sick, and to bestow alms on them, and assist them.
Many miracles are said to have been wrought in that place, or with the dust carried from it; but we have thought it sufficient to mention two, which we have heard from our elders.
It happened, not long after his death, that a man was travelling on horseback near that place, when his horse on a sudden fell sick, stood still, hung his head, and foamed at the mouth, and, at length, as his pain increased, he fell to the ground; the rider dismounted, and taking off his saddle,waited to see whether the beast would recover or die. At length, after writhing for a long time in extreme anguish, the horse happened in his struggles to come to the very place where the great king died. Immediately the pain abated, the beast ceased from his frantic kicking, and, after the manner of horses, as if resting from his weariness, he rolled from side to side, and then starting up, perfectly recovered, began to graze hungrily on the green herbage. The rider observing this, and being an intelligent man, concluded that there must be some wonderful sanctity in the place where the horse had been healed, and he marked the spot. After which he again mounted his horse, and went on to the inn where he intended to stop. On his arrival he found a girl, niece to the landlord, who had long been sick of the palsy; and when the members of the household, in his presence, lamented the girl’s grievous calamity, he gave them an account of the place where his horse had been cured. In brief, she was put into a wagon and carried to the place and laid down there. At first she slept awhile, and when she awoke, found herself healed of her infirmity. Upon which she called for water, washed her face, arranged her hair, put a kerchief on her head, and returned home on foot, in good health, with those who had brought her.