פירוש על פסחים 42:14

...It was cinged before its time of biur hametz - he is allowed to derive benefit even after the time - For example, that is disqualified from being eaten by a dog, that in any other manner - this would not be allowed (to derive benefit). This is similar to the case of bread that became spoiled cite in the first chapter of Pesachim (15B).

...No, it is necessary - When the mishna say it is allowed, we are referring to after the time of burning the hametz, for example - the hametz was cinged with a good fire before its time that resulted in abolishing its taste and appearance.