Not only it is illegal[1] to discriminate based on religion when hiring people, it is also unproductive because you're stopping yourself from hiring people to do a job based on their beliefs not their skills.
Your username is "sciencelover". I assume therefore that you are opposing Christianity to science. Let me help you reconsider this position by suggesting you to look at this article listing Christians in science and technology (You might be surprised to see some significative amount of famous scientists like Lavoisier, Pasteur, Newton, James Clerk Maxwell and many many others): https://en.wikipedia.org/wiki/List_of_Christians_in_science_...
[1] https://www.eeoc.gov/prohibited-employment-policiespractices....