In the time of the Goths, when the most blessed man John, Bishop of this church of Rome, travelled to the Emperor Justinian the elder, he came into the country of Corinth, where he lacked a horse to ride upon: which a certain nobleman understanding, lent him that horse which, because he was gentle, his wife used for her own saddle, with order that when he came where he could provide himself of another, his wife’s horse should be sent back again.
And so the Bishop rode upon him, until he came to a certain place where he got another, and then he returned that which he had borrowed. But afterward, when his wife came to take his back, as before she used, by no means could she do it, because the horse, having carried so great a Bishop, would not suffer a woman to come any more upon his back, and therefore he began with monstrous snorting, neighing, and continual stirring, as it were in scorn, to shew that he could not bear any woman, upon whom the Pope himself had ridden: which thing her husband wisely considering, straightways sent him again to the holy man, beseeching him to accept of that horse, which by riding he had dedicated to his own service.
Of the same man, another miracle is also reported by our ancestors: to wit, that in Constantinople, when he came to the gate called Aurea, where he was met with great numbers of people, in the presence of them all, he restored sight to a blind man that did instantly crave it: for laying his hand upon him, he banished away that darkness which possessed his eyes.
From “Gregory the Great, Dialogues”