The Murrell-Fueno type of the intermolecular perturbation approach was applied to the acid-catalyzed hydrolysis of diformamide. The results show that: (1) the attack of a water molecule on the protonated carbonyl carbon is favored over that on the unprotonated carbonyl carbon; (2) the ${sigma}$-approach model of water is preferred to the ${pi}$-approach model; (3) the major contributing term to the total energy is the Coulomb energy, $E_q$, especially in the ${sigma}$-approach, while the contribution of $E_{ct}$ (and $E_k$) increases moderately in the ${pi}$-approach; (4) the reaction is a charge-controlled one, a hard-hard type in the language of the HSAB principle.