Of the election of Ambrosius, the Bishop of Milan
Thus spoke the emperor, and then the council begged him, being a wise and devout prince, to make the choice. He then replied, “The responsibility is too great for us. You who have been dignified with divine grace, and have received illumination from above, will make a better choice.” So they left the imperial presence and began to deliberate apart. In the meanwhile the people of Milan were torn by factions, some eager that one, some that another, should be promoted. They who had been infected with the unsoundness of Auxentius were for choosing men of like opinions, while they of the orthodox party were in their turn anxious to have a bishop of like sentiments with themselves. When Ambrosius, who held the chief civil magistracy of the district, was apprised of the contention, being afraid lest some seditious violence should be attempted he hurried to the church; at once there was a lull in the strife. The people cried with one voice “Make Ambrose our pastor,”— although up to this time he was still unbaptized. News of what was being done was brought to the emperor, and he at once ordered the admirable man to be baptized and ordained, for he knew that his judgment was straight and true as the rule of the carpenter and his sentence more exact than the beam of the balance. Moreover he concluded from the agreement come to by men of opposite sentiments that the selection was divine. Ambrose then received the divine gift of holy baptism, and the grace of the archiepiscopal office. The most excellent emperor was present on the occasion and is said to have offered the following hymn of praise to his Lord and Saviour. “We thank you, Almighty Lord and Saviour; I have committed to this man's keeping men's bodies; You have entrusted to him their souls, and hast shown my choice to be righteous.”
Not many days after the divine Ambrosius addressed the emperor with the utmost freedom, and found fault with certain proceedings of the magistrates as improper. Valentinian remarked that this freedom was no novelty to him, and that, well acquainted with it as he was, he had not merely offered no opposition to, but had gladly concurred in, the appointment to the bishopric. “Go on,” continued the emperor, “as God's law bids you, healing the errors of our souls.”
Such were the deeds and words of Valentinian at Milan.
Source: Ecclesiastical History (New Advent)