What do these three words have in common polish, job, herb?

They are all heterophones.

"In linguistics, heterophones are words that are spelled the same but have different pronunciations and meanings, such as desert (abandon) and desert (arid region). Heterophones are a type of homonym, and are also called heteronyms."
https://en.wikipedia.org/wiki/Heterophone

So, the Polish noblewoman orderd the maid to polish the silver.
The long-suffering Job made a great job of bearing his affliction.
Herb tossed a lovely salad of greens and herbs.

They are each pronounced differently if the first letter is capitalized.

Polish/polish
Job/job
Herb/herb

They are all capitonyms which are words that change their meanings (and sometimes their pronunciation) when capitalized. Other examples include august china, and catholic.

https://en.wikipedia.org/wiki/List_of_case-sensitive_English_words

Well, I do believe maninmidohio's got it. We must share these poems from his reference:

Job's Job
In August, an august patriarch
Was reading an ad in Reading, Mass.
Long-suffering Job secured a job
To polish piles of Polish brass.

Herb's Herbs
A herb store owner, name of Herb,
Moved to a rainier Mount Rainier.
It would have been so nice in Nice,
And even tangier in Tangier.