Whenever under the provisions of the laws of this state a district obtains money or credits from the issuance of its bonds or other evidence of indebtedness for the purpose of the purchase, construction or extension or repair of district utilities in the district, it shall be unlawful to divert, use or expend any of the money or credits in the purchase, construction or extension or repair of any other water, sewer or fee-for-service system or for any purpose other than that for which the money or credits were obtained.