On today’s daf, the Gemara quotes a teaching from Rabbi Shimon ben Elazar about vows concerning fish.
(A person who says): “Fish [dag] I will not taste,” is prohibited from large ones and permitted to small ones.
(A person who says), “Fish [daga] I will not taste,” is prohibited from small ones and permitted to large ones.
In our day, we typically use the word fish to refer to a wide variety of species, both large and small. But Rabbi Shimon ben Elazar’s ruling is based upon the notion that, in his day, people referred to large fish by the word dag and small fish by the word daga. So if you want to vow to prohibit yourself from eating all fish, he requires that you use both words. If you don’t, you’ll only be prohibited from eating one size or the other.
In response, Rav Pappa asks about the origins of these various terms, and Abaye provides this answer:
It is written: “And the Lord prepared a fish [dag] to swallow up Jonah.” (Jonah 2:1)
This answer might be a surprise to those who grew up on the tradition that the prophet Jonah was swallowed by a whale. But the verse actually says it was a fish (dag). And if that fish was big enough to swallow the prophet whole, it must have been a fish of great size.
Seems like a pretty solid citation, but the Gemara isn’t buying it:
But isn’t it written in the following verse: “Then Jonah prayed to the Lord his God out of the belly of the fish[daga].” (Jonah 2:2)
In the very next verse, the fish, which is labeled dag in verse one, is called daga, suggesting that both dag and daga can refer to a large fish. The Gemara attempts to resolve the issue this way:
This is not difficult, as perhaps a large fish spat him out and a small fish then swallowed him.
It’s possible, suggests the Gemara, that the Bible holds by Rabbi Shimon’s definitions. But if it does, we need to read the story in a way that sticks to them. This would mean that Jonah is swallowed twice, first by a dag in verse 1, which then proceeds to spit him out, and then by a daga in verse 2.
Perhaps sensing this is an untenable reading, the Gemara turns to another biblical verse that describes the Nile River after the plague that turns it to blood: “And the fish [daga] that were in the river died.” (Exodus 7:21)
Like the first verse from Jonah, this one also suggests that daga can refer to fish both great and small. How so? Well, if the Nile turned to blood and was inhospitable to fish, is it possible that only the small fish died? No, says the Gemara, the big fish must have died too. And so, once again, the word daga refers to fish of any size.
All of which seems to leave Rabbi Shimon ben Elazar in a bind. On what basis then does he claim that dag is a large fish and daga is a small fish? The Gemara concludes:
With regard to vows one should follow the language of people.
As we’ve seen now several times in Nedarim, the Gemara holds that when a person makes a vow, it should be understood in the common language of the people. If the common usage is that dag means big fish and daga means little ones, Rabbi Shimon’s standard makes sense, even if the biblical sources suggest otherwise.
If this conclusion sounds familiar, that’s because we saw a similar discussion on Nedarim 49 and Rosh Hashanah 12 (and we’ll see this principle invoked again on Bekhorot 55 and Ararkhin 19). This is not out of the ordinary for the Talmud, which does the same for a number of other principles as well. Yet, Tractate Nedarim feels uniquely repetitive. Perhaps that is because it has a narrow subject — the utterance of vows — which keeps us focused on questions of what exactly vows mean and whether they are legally binding.
One of the joys of Talmud study is seeking out the unique and interesting on every page — like a deep dive into a word we thought was familiar. But when you’re swimming in the sea of Talmud for seven years, you’re going to have a range of experiences, and as a recreational fisherman might tell you, sometimes it’s also about the journey and not the catch of the day.
Read all of Nedarim 51 on Sefaria.