"in essentials, unity; in doubtful matters, liberty; in all things, charity."
Chances are, you have seen this quote in some variation of wording. Many churches use it as a sort of 'unity' motto and print it on bulletins and signs. The quote is usually attributed to Augustine but a professor at Georgetown University, who is an Augustine scholar, says he cannot find it attributed to him anywhere. In this piece, the professor gives us some background on this quote and it's earliest known usage.
The background on this quote is very interesting and I highly recommend you read it. My only question in using this quote in any form is what do we consider a 'non-essential'? And can there be unity on the answer! (tongue planted firmly in cheek)
A special thanks to Jim at Old Truth for bringing this up and finding the Georgetown University Research.