I think this is C.S. Lewis (correct me if I'm wrong)

In non-essentials, liberty
In essentials, unity
In all things charity

(note: charity has a connotation of giving, C.S. Lewis does'nt use it that way, Charity for him is another word for love. You would have to read Mere Christianity to understand what he means by charity, but it is almost a synyomn for love.)