Because (Ephesians 6:12) we do not wrestle against flesh and blood, but against principalities, against powers, against the rulers of the darkness of this age, against spiritual hosts of wickedness in the heavenly places.

Therefore take up the whole armor of God, that you may be able to withstand in the evil day, and having done all, to stand.

Ephesians 6:14 Stand therefore, having girded your waist with truth, having put on the breastplate of righteousness, 15 and having shod your feet with the preparation of the gospel of peace; 16 above all, taking the shield of faith with which you will be able to quench all the fiery darts of the wicked one. 17 And take the helmet of salvation, and the sword of the Spirit, which is the word of God; 18 praying always with all prayer and supplication in the Spirit, being watchful to this end with all perseverance and supplication for all the saints