I really like that verse. I'm glad you shared it.
The word that is translated as “rabbis” is أَحْبَارَهُمْ /a7bārahum/ and it has a larger meaning that just “rabbis”. I also interpret it as scholars or people who read and write Scriptures.
It has cognates in other Semitic languages and can definitely mean any of those.
I was unable to find the word in pre-Islamic Arabic Poetry but it isn't surprising that a people who couldn't read or write wouldn't talk about those who read and write in their poetry.
أَحْبَار
/a7bār/
Root: ح-ب-ر
(7-b-r)
Cognates: