Ephesians 6:12 For our struggle is not against flesh and blood, but against the rulers, against the authorities, against the powers of this dark world and against the spiritual forces of evil in the heavenly realms.

Ephesians 6:12-17 makes especially clear that we are involved in a war, a spiritual war, and thus our weaponry must also be spiritual. The Christian must tend to his weapons, as every soldier in warfare must, for not only is his life on the line but also the lives of his buddies, as he is their keeper too.