No corporation established under this chapter shall directly or indirectly make a loan or discount on the security of the shares of its own capital stock, nor be the purchaser or holder of such shares, unless such security or purchase shall be necessary to prevent loss upon a debt previously contracted in good faith. The stock so purchased or acquired shall, within 6 months after its purchase or acquisition, be sold or disposed of at public or private sale. Notwithstanding the foregoing, the Commissioner may approve the purchase by such a corporation of the shares of its own capital stock, subject to such terms and conditions, if any, as the Commissioner may require.