If proof of the execution of an instrument is made by a subscribing witness, such witness must be known personally to the officer taking the proof to be the person whose name is subscribed to the instrument as a witness or must be proved to be such by the oath of a credible witness. The subscribing witness must prove that the person whose name is subscribed to the instrument as a party is the person described in it, that such person executed it, and that the witness subscribed the witness’s name thereto as a witness.