"To God Be The Glory" is a common phrase I see in many places, but when I type it on Word, it suggests it to be "To God Is The Glory". Is "be" in the phrase grammatically incorrect?
In this context, I think be is the preferable word over is.
The phrase means, essentially, "May all the glory be ascribed to God."
One could use is and still be grammatically correct – as in, "All the glory is ascribed to God" – however, humankind seems to have trouble doing that on a consistent basis. That's why we usually say the former (which expresses a hope for a desired state) rather than the latter (which expresses a seldom-observed statement of fact).