On today’s daf, we learn that if you want to make a vow through comparison, you have to compare apples to apples — not to oranges. How so? If you want to vow that meat is prohibited to you through comparison, you have to compare it to something else that is prohibited through a vow.
One said: I hereby (declare) that I will not eat meat and I will not drink wine (today) like the day his father died; or like the day his teacher died; or like the day Gedaliah, son of Ahikam, was killed; or like the day I saw Jerusalem in its destruction.
Each of these is a profound personal or communal tragedy — the death of a parent or teacher, the assassination of the leader of the Judean community at the start of the Babylonian exile, or the destruction of Jerusalem. And each is a moment when one might vow to mark the occasion by diminishing one’s comfort or luxury. In fact, communally we still mark both the assassination of Gedaliah and the destruction of the Temple annually with days of fasting.
So if you want to vow to abstain from meat or wine, you can compare your vow to another vow to avoid the finer things in life. But this doesn’t work if you compare your vow to something that is prohibited in some non-vow-related way. Ravina gives an example:
Like the challah of Aaron, or like his terumah, it is permitted.
Challah refers to the portion of dough given to the priests and terumah refers to the portion of produce given to the priests. These items are prohibited to non-priests not through vows, but through Torah law. This is an apples to oranges comparison, equating something given up through a vow to something you were never entitled to in the first place, which just doesn’t work. As a result, whatever you’re vowing is going to be prohibited to you — isn’t.
Two things are worth pointing out here. First, it’s probably better not to compare when making a vow but just to say: This thing is forbidden to me. Given all the complications we’re learning about in this tractate, if you’re going to vow, better to be as clear as possible.
Second, Ravina lived over 300 years after the destruction of the Temple. The Temple and its service were as distant from his lifetime as the Continental Congress that created the United States is from our own. And yet, the world he’s describing is one in which the different types of terumah given to priests are as alive in the discourse as something that happened yesterday.
According to this discussion, vowing by comparison to the challah of Aaron doesn’t work not because we don’t understand the frame of reference, but because (apparently) everyone knows that it is prohibited by Torah law, not a vow. This is a world where the Jewish past is the Jewish present, and it shapes the Jewish future with particular laws about what kinds of vows work.
With such a live understanding of their own history, the rabbis urge caution against making comparisons that don’t hold up. Details matter. But while the text assumes that everyone knows these Temple minutiae, I think we can assume that many people in late antiquity (like today) actually didn’t. The rabbinic discussion doesn’t address that lack of knowledge — vows work (or don’t work) based on the words we use, whether or not we understand their history. And given the high expectation of halakhic, historical and linguistic knowledge that they require, it’s probably better not to vow at all.
Read all of Nedarim 12 on Sefaria.