What if you brought someone back from Arabia in 600 AD and you spoke Arabic? Would you be able to understand them? How much have languages such as Hebrew and Arabic changed over the last 2000 years?
It’s a bit different, but I can give you answer for French.
The first text we have written in a distinctively Romance language, considered to be the first trace of a French language, is the oaths of Strasbourg, a treaty of alliance between the sons of Louis the Pious. It is dated from 842. The Romance part (the text is also in latin and germanic) is very close to vulgar latin, and completely unintelligible for a modern day French speaker.
The part in Romance language:
“ Pro Deo amur et pro christian poblo et nostro commun salvament, d'ist di en avant, in quant Deus savir et podir me dunat, si salvarai eo cist meon fradre Karlo et in aiudha et in cadhuna cosa, si cum om per dreit son fradra salvar dift, in o quid il mi altresi fazet, et ab Ludher nul plaid nunquam prindrai, qui meon vol cist meon fradre Karle in damno sit. “
Translated in modern day French:
“ Pour l'amour de Dieu et pour le peuple chrétien et notre salut commun, à partir d'aujourd'hui, autant que Dieu me donnera savoir et pouvoir, je secourrai ce mien frère Charles par mon aide et en toute chose, comme on doit secourir son frère, selon l'équité, à condition qu'il fasse de même pour moi, et je ne tiendrai jamais avec Lothaire aucun plaid qui, de ma volonté, puisse être dommageable à mon frère Charles. “
Source: Naissance de la littérature française, Philippe Walter.
Specifically Hebrew- there would be a BIG difference between written and spoken Hebrew.
Written Hebrew really hasn't changed much, let's say since 600 AD as you used that date above for Arabic. I discuss this more here.
While there would be a problem with modern Hebrew as words have been added, there are enough similar words that communication wouldn't be a problem, and as many of those modern words are really just words for modern ideas/inventions, a big chunk of the problem would actually just be trying to explain modern phenomena to someone in the past!
As far as conversation, the real issue is pronunciation. u/gingeryid (or, as he was then called, u/gingerkid1234) wrote about this a while back here. On a practical level, YMMV on how similar the two are- as a Hebrew speaker myself, I can say that, having listened to recordings of Tiberian (late ancient/early medieval) Hebrew (such as those here), it's not too difficult to understand.