“Worry is the intrest paid by those who borrow trouble.”

To mothers, who were worried about the fate of their children. Quoted in "Gestapo: Instrument of Tyranny" - Page 118 - by Edward Crankshaw - History - 1956

On The Fiscal Crisis Of The 1970s. Quoted in an interview by PBS http://www.pbs.org/wnet/newyork/series/interview/dinkins.html

Source: Space Chantey (1968), Ch. 5, on Polyphemia
Context: Roadstrum had always believed that he had troubles enough of his own. He seldom borrowed trouble, and never on usurious terms. He knew that it was a solid thing that sheep do not gather in taverns and drink beer, not even potato beer; that they do not sing, not even badly; that they do not tell stories. But a stranger can easily make trouble for himself on a strange world by challenging local customs.
"But I am the greet Roadstrum," he said, suddenly and loudly. "I am a great one for winning justice for the lowly, and I do not scare easily. I threw the great Atlas at the wrestle, and who else can say as much? I suffer from the heroic sickness every third day about nightfall, and I am not sure whether this is the third day or not. I say you are men and not sheep. I say: Arise and be men indeed!"
"It has been tried before," said Roadstrum's friend, the sheep, "and it didn't work."
"You have tried a revolt, and it failed?"
"No, no, another man tried to incite us to revolt, and failed."

Tripadis

Although this appears in Pollard's Connotary in 1932, the aphorism was already in general circulation decades earlier, e.g., it features in an advertisement in The Grape Belt, 2 October 1906, p. 5 http://news.google.com/newspapers?id=LY9CAAAAIBAJ&sjid=tLkMAAAAIBAJ&pg=5967,3394664&dq=worry-is-interest-paid-on-trouble-before-it-falls-due&hl=en. It is also widely misattributed to Dean Inge.
Misattributed

Source: Redemption Ark (2002), Chapter 34 (p. 628)