Full Idea
Of all the things which wisdom provides for the happiness of the whole life, by far the most important is the acquisition of friendship.
Gist of Idea
Friendship is by far the most important ingredient of a complete and happy life
Source
Epicurus (fragments/reports [c.289 BCE]), quoted by Diogenes Laertius - Lives of Eminent Philosophers 10.31.28
Book Reference
Diogenes Laertius: 'Diogenes Laertius', ed/tr. Yonge,C.D. [Henry G. Bohn 1853], p.477