MEGILLAT SETARIM (Heb. מְגִלַּת סְתָרִים; lit. "concealed scroll"). On two occasions (Shab. 6b; bm 92a), *Rav mentions that he found a Megillat Setarim in the academy of R. Ḥiyya containing laws in the name of Isi b. Judah. The first is that there are 39 principal categories of work (avot melakhah) forbidden on the Sabbath, but culpability is incurred only on account of one (this is the actual statement quoted, although the Talmud finds it inconceivable and emends it to "there is one for which culpability is not incurred"). In the second he states that the law in Deuteronomy 23:25, "When thou comest into thy neighbor's vineyard, then thou mayest eat grapes until thou have enough at thine own pleasure," applies to anyone entering the vineyard, and not only to a laborer employed there, on which Rava commented, "Isi would make it impossible to live," since a man would soon have his vineyard stripped, and there also the statement is then qualified as a result.
Rashi (ad. loc.) explains that the scroll was concealed because it was forbidden in general to commit the Oral Law to writing but since these laws were not generally taught, they were written down to save them from oblivion. I.H. Weiss is of the opinion that they contained views which Judah ha-Nasi rejected, and they were kept concealed out of respect for him, but this view is most improbable. All the beraitot were excluded from the Mishnah, and they contained many views that he had rejected, yet there is no suggestion that they were suppressed. Kaplan maintains that these scrolls were kept concealed because their contents were unsuitable for publication, and in addition he suggests that "concealed" means that they were written in a cryptic manner to conceal their meaning. However, there is nothing particularly cryptic in the language of the passages quoted. Nevertheless, it certainly would have been dangerous to make these laws widely known, and that would also explain why these are the only laws mentioned.
I.H. Weiss, Dor, 2 (19044), 168–9; M. Kaplan, Redaction of the Babylonian Talmud (1933), 277–8.