Tradition
St. Ambrose
Letters
Book 40 › Section 27
27. But at any rate if too little confidence is placed in me, command the presence of those bishops whom you think fit, let it be discussed, O Emperor, what ought to be done without injury to the faith. If you consult your officers concerning pecuniary causes, how much more just is it that you should consult the priests of God in the cause of religion.
Source: Letters (New Advent)