The present research is to expound and analyze juristic proofs of a fatwa by imam khomaini. The fatwa is concerning prodigality in the use of water and electricity including two precepts of prohibition and liability, since that fatwa can be applied to similar cases such as gas on the one hand and plays a significant role in economic development of our country on the other, exposition of proofs of both precepts becomes necessary. Four reasons for prohibition and three juristic rules for liability are presented here. In this essay it becomes clear that such a fatwa is not a secondary precept; rather, it is based on juristic rules and proofs and is a primary precept.
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