There is no limit to what a man can do so long as he does not care a straw who gets the credit for it.

Charles Edward "C. E." Montague (1867–1928) English journalist, novelist, essayist

“Any Cure?” sec. 3, Disenchantment (1922)
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Montague did not take credit for the phrase, referring to it as a saying.

This was not the first time Montague used the phrase. In a memoir about journalist William T. Arnold in 1906, he stated that a phrase that "someone has said" was a particular favorite of Arnold's: "There is no limit to what a man can do who does not care who gains the credit for it."

More discussion of the quote and its origins: A Man May Do an Immense Deal of Good, If He Does Not Care Who Gets the Credit – Quote Investigator. See also Truman.