By Theodoret of Cyrus
A certain horse of good breed and trained to be an excellent mount was particularly dear to the emperor [Valens]. To the great distress of the emperor it caught a disease: its secretion of urine was blocked. Those trained in the skill were summoned to tend it; but to the distress of the emperor and the grief of the man entrusted with the care of the horses, their skill was defeated. Being pious and strong in faith, he repaired at midday to the dwelling of the great Aphrahat [the Persian]. After mentioning the disease and declaring his faith, he besought him to dispel the complaint by prayer. Without delaying for a moment but instantly beseeching God, he ordered water to be drawn from the well, and making on this the sign of the cross of salvation gave instructions for it to be given to the horse, which, contrary to its habit, drank it. Then consecrating oil by the invocation of the divine blessing, he anointed the horse's belly: at the touch of his hand the disease immediately departed and at once natural secretion took place. In great joy the man took the horse and ran back to the stable. In the evening the emperor, who was in the habit of visiting the stable at this time, came and asked how the horse was. When the man told of his good health and led the horse out, vigorous, prancing, neighing, and holding his neck up proudly, he inquired after the cause of health. After evading reply several times - for he feared to indicate the doctor, knowing the enmity of the questioner - he was finally forced to tell the truth and told of the manner of cure. The emperor was astonished and agreed that the man was remarkable. However, he was not freed of his earlier madness, but persisted in raging against the Only-begotten until he became a casualty of a fire lit by barbarians and did not even receive a burial like servants or beggars.
From A History of the Monks of Syria.