Does my employer have to pay my holiday pay when I leave?

Generally, you are entitled to all benefits you earned during the course of your employment. To fully answer this question, though, we would need to see what the employment handbook reads. While the employment handbook does not trump VA law, it can explain what the employer is contemplating.

However, in answer to your question, the code section in question is VA Code 40.1-29. While the employer is not required to pay holiday, personal, or sick days, once they agree to do so as part of your employment package, it becomes part of your wages.