Lyndon Johnson actually said...
So, this is our pledge to the memory of this great man who is really, as all of you here know, a true citizen of the world--a pledge to devote our energies and our talents and our resources and our wills to the cause for which he died.
Context
Remarks at a Luncheon for Members of the Joint U.S.-Japan Committee on Trade and Economic Affairs
07/13/1965