All refunding bonds issued under the provisions of Sections 31-15-1 through 31-15-19 shall be general obligations of the political subdivisions issuing same, and the governing authority of such subdivision shall annually levy a tax upon all taxable property therein sufficient to pay the principal of and the interest on such bonds as the same matures and accrues. The full faith, credit, and resources of such subdivision shall be and are hereby irrevocably pledged to the payment of such bonds, both as to principal and interest.