2,659. An Oath Not to Eat Dates or Treif

Hilchos Shevuos 5:10

Let’s say that someone took an oath not to eat dates, neveila or treifa. If he ate an olive’s volume of neveila or treifa, he’s also liable for an oath of expression because he included prohibited items alongside permitted items. Once the oath takes effect vis-à-vis dates, it also takes effect vis-à-vis those prohibited items, as was discussed in halacha 4:11.

Hilchos Shevuos 5:11

However, if someone took an oath not to eat neveila, treifa, etc., there’s no obligation of an oath at all – neither an oath of expression nor an oath in vain – regardless of whether he ate the thing or not.