Riddle: Name a halacha derived from a statement of Satan.
closed as not a real question by Isaac Moses Jun 16 '11 at 22:08
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The statement is Job 2:4
The Halacha is that while we may not redeem a captive if the price is too high, an individual is entitled to spend as much of his own money as he likes on redeeming himself (and possibly his spouse). This is based on the above verse. --Tosfos, Kesubos 52a, s.v. והיו.
My understanding of Tosfos is that the verse is describing a reality of human behavior. Since: