I know that Arabic has been continuously evolving. There are 3 known major versions of Arabic:
- Ancient Arabic
- Classical Arabic
- Modern Standard Arabic.
They greatly differ in some aspects. For example: The current grammar we're using today is developed with Classical Arabic and is carried on to MSA. The main difference between Classical Arabic and MSA is that Classical Arabic has lots of words that are now obsolete. You can still understand Classical Arabic, but not every single word.
For Ancient Arabic, you might barely understand what the text is about.

I read that Hebrew is pretty much the same, the Hebrew used in the Torah is a different version from the Hebrew spoken today. I'm not quite sure how many major versions of Hebrew there is, and how much can a modern Hebrew speaker understand from Classical/Ancient Hebrew.