2,658. An Oath Not to Eat Dirt

Hilchos Shevuos 5:8

If someone takes an oath to eat smaller than an olive’s volume of neveila or treifa, he can be liable for violating an oath of expression. If he takes an oath not to eat earth and similar things that aren’t fit for consumption, and then he eats an olive’s volume of that thing, he’s liable; if he ate less than this, it’s a case of doubt. One might be liable for eating even the smallest volume; since these things aren’t typically eaten, the normal volumes of food might not apply.

Hilchos Shevuos 5:9

Similarly, if one takes an oath not to eat grape seeds and he eats less than an olive’s volume of them, it’s a case of doubt. If the one who took the oath was a nazir, who is prohibited from eating an olive’s volume of grape seeds, he is exempt for an oath of expression if he ate smaller than an olive’s volume since his intention in taking the oath was only regarding the olive’s volume in which he was already liable, with the result that the oath is not effective. Accordingly, if someone took an oath not to eat even a single grape seed, he would be liable for eating it.