Quote by Robert F. Kennedy

Few men are willing to brave the disapproval of their fellows, the censure of their colleagues, the wrath of their society. Moral courage is a rarer commodity than bravery in battle or great intelligence. Yet it is the one essential, vital quality for those who seek to change a world which yields most painfully to change.

Please suggest source details if you know: book, page, year, online article address (url), correction (different author...), etc.. Thanks.