2,657. An Oath Not to Eat Non-Kosher Foods

Hilchos Shevuos 5:6

If someone took an oath that he didn’t eat, and he had eaten things that aren’t fit for consumption, or he partook from neveila, treifa, etc., he’s liable. Eating them is considered eating because they’re significant to him, which is easily inferred from the fact that he ate them. When it comes to the future, however, such as if he took an oath not to eat and then he ate these things in an usual turn of events, that’s not considered eating, as was explained in halacha 5:5.

Hilchos Shevuos 5:7

Let’s say that someone takes an oath not to eat even the smallest volume of neveila or treifa, after which he ate smaller than an olive’s volume. In such a case, he’s liable for taking a false oath because one isn’t bound by an oath from Sinai for half the requisite volume.