[IDEM libro sexto iuris epitomarum. ] §46.1.65.prSicut reus principalis non alias, quam si de sua persona promittat, obligatur, ita fideiussores non alias tenentur, quam si se quid daturos uel facturos promittant: nam reum principalem daturum uel facturum aliquid frustra promittunt, quia factum alienum inutiliter promittitur.
Just as the principal debtor is not bound otherwise than if he promises in respect of his own person, so sureties are not bound otherwise than if they promise that they themselves will give or do something: for they promise in vain that the principal debtor will give or do something, because the act of another is promised without effect.