56-1-9. Holder of instrument for the payment of money, upon which third person liable, transferring it in payment of precedent debt entering into a promise respecting such instrument--Writing unnecessary.
A promise to answer for the obligation of another is deemed an original obligation of the promiser and need not be in writing where the holder of an instrument for the payment of money, upon which a third person is or may become liable to him, transfers it in payment of a precedent debt of his own or for a new consideration, and in connection with such transfer enters into a promise respecting such instrument.
Source: SDC 1939, §26.0105 (5).