[1] Daniel, the eldest, seems to have composed a commentary on the Mishnaic section Zeraim, from which the Arukh quotes frequently and to have stood in friendly relations with Christian scholars.
Aside from the Arukh of Tzemach ben Poltoi, which he utilized (it should be stated, however, that Solomon Judah Loeb Rapoport and Abraham Geiger deny this), he used a vast 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.
None can gainsay the author's philologic spirit of inquiry – quite remarkable for his day, which antedated the science of linguistics; his frequent collation of "variæ lectiones" is notable, while his fine literary sense often saved him from crude etymological errancies.
For this reason, the various dialects appear in the Arukh under several names, each originating seemingly in a different author, as Arabic, for example, which occurs under three distinct denotations, possibly without Nathan being aware of their synonymity.
To the exact cause may be assigned the polyonymy of the Hebrew and rabbinic dialects in the Arukh and the presence of a great deal of geographic and ethnographic information that the author did not acquire in actual travel.
Aside from its purely scientific value as a storehouse of old readings and interpretations as well as of titles of many lost books, it is important as the only literary production of the Italian Jews of that age.
Compiled at the historical juncture when Jewish scholarship was transplanted from Babylonia and northern Africa to Europe and was subject to aberration, it signally emphasized the necessity of preserving the old rabbinical treasures and traditions.
Its service in this respect was equivalent to that rendered by the two great products of contemporary Spanish and French Jews – Alfasi's Talmudic code and Rashi's commentary.
Since its author, for example, uses the Italian language freely to elucidate etymologies, he frequently offers the vernacular nomenclature for objects of natural history that he repeatedly calls into service for purposes of illustration of the customs of foreign peoples, the character of the reading public of his day can easily be inferred.
According to Kohut, even Rashi was already in a position to utilize it in the second edition of his commentaries, having been acquainted with it by Kalonymos ben Sabbatai, the noted rabbi who had moved to Worms from Rome.
Kalonymus, however, can at best have transported to his new home but meager information concerning the Arukh, as his removal occurred about thirty years before its completion, the first folios he may have seen since he was intimately acquainted with Nathan.
The first supplement was written in the 12th century by R. Samuel ben Jacob ibn Jam'i or Jama'[5] of Narbonne, under the title Agur,[6] a small work of little significance.
At the beginning of the 16th century, Abraham Zacuto, author of the Yuḥasin, composed a supplement entitled Iḳḳere ha-Talmud, of which only a fragment of the latter part has survived.
About the same time, Santes Pagnino, a Christian and friar of the Dominican Order, issued an Enchiridion Expositionis Vocabulorum Haruch, Thargum, Midraschim Rabboth, et Aliorum Librorum.
[7] The general method of the Arukh was also adopted by Elia Levita, who, in his Meturgeman and Tishbi, advanced a step in that he differentiated the targumic and the Talmudic words and also sought to complete his prototype.
Mussafia's Musaf he-'Arukh (1655), probably known also as Arukh he-Hadash, according to Immanuel Löw, devoted itself mainly to Greek and Latin derivatives, leaning largely on Johannes Buxtorf.