John Naughton has published this here and here:

The physicist I.I. Rabi and General (later President) Dwight Eisenhower became friends after Eisenhower was appointed president of Columbia University soon after the end of WW2. When introduced to Rabi, Eisenhower said, “I am always very happy to see one of the employees of the university,� to which Rabi replied, “Mr. President, the faculty are not the employees of the university. They are the university.�

Quoted in J. S. Rigden, Rabi: Scientist and Citizen, Harvard University Press, 2000.