The refunding bonds, and interest thereon, shall not be a debt of the public body, nor a charge, lien or encumbrance, legal or equitable, upon any property of the public body, nor upon any income, receipts, or revenues of the public body other than such of the revenues of the enterprise as shall have been pledged to the payment thereof, and every refunding bond shall recite in substance that said bond, including interest thereon, is payable solely from the revenues pledged to the payment thereof and that the public body is under no obligation to pay the same, except from said revenues.