Ambrose, Bishop, to the most gracious Emperor Eugenius.
1. The cause of my departure was the fear of the Lord, to Whom, so far as I am able, I am accustomed to refer all my acts, and never to turn away my mind from Him, nor to make more of any man than of the grace of Christ. For I do no one an injury, if I set God before all, and, trusting in Him, I am not afraid to tell you emperors my thoughts, such as they are. And so I will not keep silence before you, O Emperor, as to things respecting which I have not kept silence before other emperors. And that I may keep the order of the matters, I will go through, one by one, the things which have to do with this matter.
Source: Letters (New Advent)