Refunding bonds and the interest thereon shall not be a debt of the municipality nor a charge, lien, or encumbrance, legal or equitable, upon any property of the municipality or upon any income, receipts, or revenues of the municipality other than such of the revenues of the enterprise as shall have been pledged to the payment thereof. Every refunding bond shall recite in substance that the bond, including interest thereon, is payable solely from the revenues pledged to the payment thereof and that the municipality is under no obligation to pay the same except from said revenues.
N.D.C.C. § 40-36-12