72 Pa. Stat. § 3958
All bonds issued under the authority of this act, shall be redeemed at maturity, and all interest due from time to time on such bonds shall be paid by the Sinking Fund Commission of the Commonwealth. For the specific purpose of redeeming said bonds at maturity and paying all interest thereon, and in accordance with the information received from the Governor as provided in section seven of this act, the General Assembly shall appropriate biennially the moneys necessary for the payment of the interest on said bonds and the principal thereof at maturity. All moneys so appropriated shall be paid into the sinking fund by the State Treasurer, and all of such moneys not necessary to pay accruing interest, shall be invested by the Sinking Fund Commission in such securities as are provided by law for the investment of the sinking funds of the Commonwealth.
The investments and such moneys and the accumulations thereon in the sinking fund shall be devoted to, and used exclusively for, the payment of the interest accruing on such bonds and their redemption at maturity: Provided, however, That the Sinking Fund Commission is authorized at any time to use any of such funds for the purchase and retirement of all or any part of the bonds issued under the authority of this act. In the event that all or any part of said bonds shall be purchased by the Sinking Fund Commission, they shall be cancelled, and returned into the State Treasury as cancelled and paid bonds, and thereafter all payments of interest thereon shall cease.
72 P.S. § 3958