One of the best books I have read over the last year is Charles Matthewes The Republic of Grace: Augustinian Thoughts for Dark Times. I have been captivated by the work he has done interpreting the implications of Augustine's thought for our day. Here is a brief sentence about authority, reflecting how Augustine speaks to those who occupy a political (and pastoral?) office:
"...whatever authority one has in office comes from God...one can prudently use one's authority only when one knows one's own sinfulness and one's temptations toward pride, and knows that one will, in the end, be judged...we borrow authority ultimately from God...the true and rightful judge" (p. 164).