Responsa Hai ben Sherira's chief claim to recognition rests on his numerous
responsa, in which he gives decisions affecting the social and religious life of the
Diaspora. Questions reached him from
Germany,
France,
Iberia,
Anatolia, the
Maghreb, and even
India and
Ethiopia. His responsa, more than 800 in number, deal with civil law, especially laws concerning women, with ritual, holidays, and so on. Many of them contain explanations of certain
halakhot,
aggadot, and Talmudic matters. In halakhic decisions he quotes the
Jerusalem Talmud, but without ascribing any authority to it. Many of his responsa may have been written in
Arabic; only a few of them have been preserved.
Legal treatises Hai ben Sherira codified various branches of Talmudic law. His works include: • An Arabic treatise on sales and transactions, translated into
Hebrew by
Isaac Albargeloni with the title
HaMekach vehaMimkar (; 1078). •
Sefer ha-Mashkon, a treatise on
mortgage law, anonymously translated into Hebrew • ''Mishpetei haTena'im,'' a treatise on conditions, also anonymously translated into Hebrew. These three treatises were published together (Venice, 1604); later editions also contain commentaries by
Eleazar ben Aryeh (Vienna, 1800) and by
Hananiah Isaac Michael Aryeh (Salonica, 1814). Another anonymous translation of them exists in manuscript under the title "Dinei Mamonot". According to Rabbi David Azulai, Hai also wrote in Arabic ''Sha'arei Shevu'ot,
a treatise on oaths. According to another Hebrew source, the original title was Kitab al-Aiman.
This treatise was twice anonymously translated into Hebrew: (1) Mishpeṭe Shebu'ot
(Venice, 1602; Altona, 1782); (2) Sefer Mehubbar be-Kotzer Min ha-Dinim be-Bi'ur Kelalim we-'liqarim be-Helqe Hiyyub la-Shebu'ah
Sha'arei Shevu'ot
was metrically arranged by an anonymous writer, probably of the 13th century, under the title Sha'arei Dinei Mamonot ve-Sha'arei Shevu'ot,'' and by
Levi ben Jacob Alkalai. Hai's treatise on boundary litigations, "Metzranut", is known only through quotations.
Hilkot Tefillin, Siddur Tefillah and
Metibot are also quoted as his.
Commentaries on the Mishnah Hai ben Sherira's
philological abilities were directed towards interpreting the
Mishnah; of this work only the portion on Seder Tohorot is extant; it was published by T. Rosenberg in "Qobetz Ma'aseh" (Berlin, 1856). This commentary contains especially interesting linguistic notes, Arabic and
Aramaic being often adduced for comparison. The author quotes the Mishnah, the two Talmuds, the
Tosefta, the
Sifra,
Targums
Onkelos and Jonathan, the
Septuagint, the works of
Saadia Gaon, the ''Sifre Refu'ah,'' and other anonymous sources. He also quotes his own commentary on
Zera'im (p. 34) and on
Baba Batra (p. 43). These quotations, and many others cited by the Arukh, prove that the commentary extended to the whole Mishnah, containing among other explanations historical and archeological notes. Some passages of the commentary are quoted by
Alfasi and
Hananel on Yoma, and by
Solomon ibn Adret in his
Hiddushim. while
Abu al-Walid ibn Janah cites Hai's commentary to
Shabbat frequently.
Other works It is uncertain whether Hai wrote commentaries in Arabic on the Bible as a whole or on parts of it.
Abraham ibn Ezra, however, in his commentary on the
Book of Job quotes several of his explanations. Hai compiled also a dictionary of especially difficult words in the
Bible, Targum, and Talmud, the Arabic title of which was
al-Hawi.
Abraham ibn Ezra translated this title, in his
Moznayim, into "Ha-Me'assef", while
Abu Bukrat's translation,
Ha-Kolel, and
Moses Botarel's translation, "Ha-Qemitzah", did not become popular. Fragments of this dictionary were discovered and published by Harkavy; these show that the work was arranged according to an alphabetic-phonetic plan of three consonants in every group; for instance, s.v. אהל it quotes the permutations אהל, אלה, הלא, האל, לאה.
Judah ibn Balaam is the earliest Jewish author who expressly quotes this dictionary.
Moses ibn Ezra and some North African rabbis of the twelfth and thirteenth centuries also mention it.
Works of disputed attribution Of Hai's poetical writings few have been preserved, and even of these the genuineness is doubted. The didactic poem "Musar Haskel" is generally regarded as authentic, though Dukes expressed some doubts as to its genuineness, as old Jewish authors like
al-Harizi and
ibn Tibbon do not mention it; and
Steinschneider also regarded it as of doubtful authenticity. The first edition appeared about 1505 (see Fano); others were published in
Constantinople (1531), in
Paris (1559), and elsewhere. The modern editions are as follows: Dukes,
Ehrensäulen, p. 96; Grätz,
Blumenlese, p. 27; Steinschneider,
Musar Haskel, Berlin, 1860; Weiss,
Liqquṭe Qadmonim, Warsaw, 1893; Philipp,
Sämmtliche Gedichte des R. Hai Gaon, Lemberg, 1881; a
Latin translation by
Jean Mercier,
Cantica Eruditionis Intellectus Auctore per Celebri R. Hai, Paris, 1561; another by
Caspar Seidel,
Carmen Morale ΣτροφορυΘμον Elegantissimum R. Chai, etc.,
Leipzig, 1638. The "Musar Haskel" consists of 189 double verses in the Arabic meter "rajaz", and it is said to have therefore received the title of "Arjuzah". If it really belongs to Hai, he was, as far as is known, the first Eastern writer to use an Arabic meter in Hebrew poetry. Every strophe is complete in itself, and independent of the preceding strophe. Some
piyyutim are ascribed to him, as the piyyut beginning with the words "Shema' qoli", preserved in the
Sephardic liturgy for the evening of
Yom Kippur. Many spurious writings have been ascribed to Hai, especially by later
kabalists. Among them are a
Sefer kol ha-Shem ba-Koah;
Pitron Halomot, Ferrara, 1552;
Sefer Refafot, ib.; ''Perush me-'Alenu
; Teshubah,
on the thirteen rules of R. Ishmael and on the Ten Sefirot; A Letter to the Priests of Africa''. Some of the responsa attributed to him are mere
forgeries. Others again were falsified or mutilated by later additions and interpolations, as, for instance, the one containing attacks upon
Aristotle and his philosophy. ==Characteristics==