Regex to match Hebrew and English characters except numbers
Seemingly Hebrew has the range \u0590-\u05fe
(according to this nice JavaScript Unicode Regex generator`.
/^[a-z\u0590-\u05fe]+$/i
While the selected answer is correct about "Hebrew" the OP wanted to limit validation to only Hebrew and English letters. The Hebrew Unicode adds a lot of punctuation and symbols (as you can see in the table here) irrelevant for such validation. If you want only Hebrew letters (along with English letters) the regex would be:
/^[a-z\u05D0-\u05EA]+$/i
I would consider adding ' (single quote) as well, for foreign consonants that are missing in Hebrew (such as G in George and Ch in Charlie) make use of it along with a letter:
/^[a-z\u05D0-\u05EA']+$/i