On Sukkah 18a, we find that lavud, a principle by which gaps of less than three are considered solid, applies to spaces along the side of the sukkah. However, Rav Acha and Ravina argue about whether it applies to gaps in the center of the (horizontal) s’chach.
וְהָנֵי מִילֵּי מִן הַצַּד. אֲבָל בָּאֶמְצַע — פְּלִיגִי בַּהּ רַב אַחָא וְרָבִינָא, חַד אָמַר: יֵשׁ לָבוּד בָּאֶמְצַע, וְחַד אָמַר: אֵין לָבוּד בָּאֶמְצַע.
Each side brings Tannaitic evidence (that it applies by the beam of an alleyway; that it doesn’t by ritual impurity) but the other side explains why that case is exceptional, so it is unclear how we should rule. We aren’t told which Amora maintains which position. However, Rif and Rosh cite a principle established in Pesachim 74b and Chullin 93b that throughout their many anonymized disputes, Ravina takes the lenient position and Rav Acha the more stringent position, and the halacha is like Ravina—except in three enumerated cases (involving whether coals draw out or locks in blood from raw red meat, testicles, and the large veins of the neck) where Rav Acha takes the lenient position, and the halacha is like Rav Acha. These three exceptions appear to be a single dispute in scientific reality, consistently applied to three cases. This principle of how to rule is often cited by Rif and Rosh their Talmudic commentaries,
The reason for this rule of psak is unclear. Do we rule like Ravina because of who he was—possibly the Talmudic redactor and the sof hora’ah? (Why would coals then be an exception? Also, Rav Acha was perhaps involved in the redaction.) Because he brought textual or scientific evidence in each case that was persuasive? (Such support is often omitted or ambiguously in both directions.) Because contemporary or later rabbinic authorities considered each case and the majority ruled like him? Or is it that these are late Amoraim analyzing earlier sources that could readily work either way, and it is therefore acceptable to always take the lenient position—כח דהיתרא עדיף?
In all these sugyot, the respective positions are unclaimed both initially (חַד אָמַר) and in the subsequent discussion (מַאן דְּאָמַר). It is curious that the redactors would not know who said what, especially if Ravina I and Rav Acha were themselves redactors (see below), but perhaps we are dealing with a later Savoraic Talmudic layer, or there is some stylistic intent at play.
Both “Rav Acha” and “Ravina” lack their patronymic (father’s name). Since many Amoraim have these names, we need to figure out which, if any, are referenced. In terms of Ravina, besides several with a patronymic or place name qualifier, historians argue whether two or three distinct figures go by plain Ravina. They examine sugyot throughout the Talmud and notice the scholastic generation of the other participants in each discourse or story. One quotes another of an (immediately) previous generation, discusses statements of prior generations, and typically argues with a contemporary or someone one generation up or down. We follow Rav Aharon Hyman that there were two Ravinas (and that where Ravina Kadmon interacts with Rav Yosef, implying an even earlier Ravina, it is the later Ravina II interacting with a Savora Rav Yosef. In turn, this impacts how we assign ambiguous Ravinas in other sugyot and the overall constructed biographies.
According to Hyman, the Ravina of our sugya is Ravina I (sixth-seventh generation, d. 421 CE), a colleague of Rav Ashi (sixth generation, 352-427 CE). His birth year is unknown, but in his youth he was a student of Rava (d. 352 CE), who calls him and Rav Chama b. Buzi “children” (Bava Batra 16b). In Eruvin 63a Ravina visits Mechoza and they want to honor him by asking him to inspect the shechita knife, but he tells them to show it to Rava. He doesn’t interact with Abaye who died 14 years earlier than Rava. His sister’s son was Ravina II (seventh generation, d. 499 CE). Ravina and Rav Ashi were sof hora’a (Bava Metzia 86a), which seems to indicate that they redacted the Talmud. According to Rashi/Rambam, Ravina I was the redactor; Sherira Gaon maintains it is Ravina II.
Hyman identifies plain Rav Acha as Rav Acha b. Rava (sixth generation, d. 419 CE). Some say his father was the famous Rava, but if so, he was born in Rava’s old age. He was a kohen, and Rav Ashi sent him pidyon haben money (Bechorot 50a, fixing the scribal error). Rava might also have been a kohen (Zevachim 9b) but Hyman argues otherwise. Together with Rav Ashi, he studied under Rav Kahana. He was extremely involved in Rav Ashi’s yeshiva in the matter of the redaction of the Talmud. In Chullin 17b, Ravina and Rav Acha b. Rava sat before Rav Ashi when people brought a shechita knife for Rav Ashi to inspect. At weddings, he would place the bride on his shoulders and dance, not worrying about negia, though did not extend his allowance to others (Ketubot 17a). He honored Rav Acha with inspecting it, and approved his method as according to Rav Kahana’s practice. In his last three years he succeeded Mar Zutra as head of Pumbedita academy.
Rabbi Dr. Joshua Waxman teaches computer science at Stern College for Women, and his research includes programmatically finding scholars and scholastic relationships in the Babylonian Talmud.