His
Risalah, a letter in Arabic but written in the
Hebrew script, to the community at
Fes (ed. Bargès and Goldberg, Paris, 1857), is the earliest known contribution to the critical study of the
Semitic languages. The work is divided into three sections, with an introduction. He warns the community not to neglect the study of the
Targumim since they are important for a correct knowledge of the
Bible, which contains many
Aramaisms. In the first section, he compares biblical words to similar Aramaic words. In the second section, he compares biblical words to later
Rabbinic Hebrew. He makes the comparison for 17 words even if they do not have a direct comparison. The third section is structured differently from the other two in that he does not deal with individual words. Instead, he deals with the larger relationship between the three Semitic languages. He explores ideas such as the interchange of letters or pronunciation, the presence or loss of certain weaker letters in roots like the
Nun, the changes of letters used in tenses, changes in gender in names and number and additional vowels or the lack thereof. An additional section is attached to the third section in which he examines the relationship between Arabic and Hebrew. In particular, he notes the alternations of
Aleph with
Ayin,
Ayin with
Ghain,
Zayin with
Dalet,
Tsade with
Teth,
Shin with
Taw, etc. He is also said to have written, in addition to the
Risalah, a dictionary and a book on the
Commandments. However, little is known about them. Although he mentions his dictionary in the
Risalah, nothing remains of it or his other book. ==Sources==