Eli ben Yehudah ha-Nazir explained

Eli ben Yehudah ha Nazir ben Zechariah, Arabic Abu Kathir Yahya al Katib ("Father of Kathir, Yahya the Scribe", fl. Tiberias, 910s), ^[1] was a grammarian and philologist of the Hebrew, Arabic and Aramaic languages. He may have been among the teachers in Tiberias of Saadia.^{[2] [3]}

His Arabic language treatise is entitled Usul al-Lugha al-'ibraniyya (c. 915) أصول اللغة العبرانيّة ("Origins of the Hebrew language").^{[4] [5]} He also commented on the opinion regarding the dagesh pronunciation of the Hebrew letter Resh as articulated by the Mazya community among earlier mesorah masters of Tiberias (c. 775-825).

References

1. Mother of reason and revelation Irene E. Zwiep - 1997 "For information on the languages spoken in the Northern parts of Israel, we may turn to Saadia's teacher Abu Kathir Yahya ben Zakariyya', also known as 'All ben Judah ha-Nazir (d. c. 920),"
2. Islamic culture through Jewish eyes p125 Esperanza Alfonso - 2008 - 201 "In the second half of the ninth century Eli ben Judah ha-Nazir, Saadia's teacher, also referred to similarities between languages
3. Abu Kathir Yahya al-Katib of Tiberias, absorbed the ideas of the Jewish philosopher
4. "'Eli ben Yehuda Hannazir and his Treatise Kitab 'Usul al-Lugha al-'ibraniyya" (hebr.), Leshonenu XXXIV (1969-70),
5. Ra'anan S. Boustan, Raʻanan S. Boustan, Oren Kosansky Jewish studies at the crossroads of anthropology and history p221 2011 "44 Among those who expressed this belief was 'Eli ben Yehudah ha-Nazir, a native of Tiberias, who wrote in a linguistic treatise of ca. 915 that when he had doubts about the accuracy of his work on the language of the Bible, .."