The Aruk
Nathan's private life was extremely sad. All his children died very young; and the bereaved father sought solace in philanthropy and scholarly application. In the year 1085 he built a communal bathhouse conforming to the ritual law; and about seventeen years later, Sept., 1101, he and his brothers erected a beautiful synagogue. In February of the latter year had been completed his magnum opus – the Aruk.
The sources of this work are numerous. Aside from the Aruk of Tzemach ben Paltzoi (Ẓemaḥ b. Palṭoi), which he utilized (it should be stated, however, that Rapoport and Geiger deny this), he used a very large number of additional works. Above all, he placed under contribution the information received, in both oral and written form, from R. Maẓliaḥ and R. Moses ha-Darshan, the former of whom, in particular, through his studies under Hai, had made himself the repository of Eastern learning. The entire extent of Nathan's indebtedness to his authorities can not be estimated, for the reason that of the hundreds of books cited by him many have not been preserved. But none will deny his obligation to R. Gershom of Mainz, whom he repeatedly quotes, though, as Kohut rightly maintains against Rapoport, he can not have been his personal disciple.
Similarly he used the writings of R. Hananeel b. Chushiel and R. Nissim ben Jacob, both living at Kairwan. So frequent, in fact, were the references to R. Hananeel in the lexicon that R. Jacob Tam, for example, regarded the work as based entirely on the commentaries of that author (Sefer ha-Yashar, p. 525), while the author of the Or Zarua, as a matter of course, referred to him almost all of the lexicon's anonymous statements.
Hai Gaon, again, figures very frequently in its pages, sometimes simply designated as "the Gaon," while it has particularly assimilated all philologic material that is contained in his commentary on the mishnaic order Ṭohorot.
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