Some 97% of the world’s Jews once spoke Arabic. 1,000 years ago to be a Jew religiously was to be an Arab linguistically.
For some 500 years the greatest minds in Judaism thought and wrote in Arabic. Maimonides’ wrote his philosophical magnum opus in Arabic.
Beginning in the 10th century, first in modern day Iraq and then in Andalusia (Spain), the Hebrew language was re-imagined through the lens of Arabic. The limited biblical vocabulary was greatly expanded by borrowing Arabic forms. The science of Hebrew linguistics was born, explicitly as an Arabic science.
In Andalusia, there was a Hebrew renaissance under the explicit influence of Arabic. Some of the most iconic Jewish prayers and poems would never have been written without the Arabic. These include Adon Olam and L’cha Dodi.
Arabic was the language of the royal courts of Cordoba It was the language of the educated man. These Arab-Jewish poets and rabbis believed they were elevating Hebrew by infusing it with Arabic.
Eve as Jews were pushed out of Andalusia and moved north into Provence and beyond, they took Arabic with them.
This was the center of world Jewry for hundreds of years leaving behind a formative legacy that defines Judaism and the Hebrew language to this day.
In other words, it is impossible to fully understand Judaism or the Hebrew language today without knowing Arabic. Arabic is the most important Jewish language after Hebrew.