"For we wrestle not against flesh and blood, but against principalities, against powers, against the rulers of the darkness of this world, against spiritual wickedness in high places" is a Bible verse from Ephesians 6:12.

In this verse, the word "principalities" conveys dignity, and "powers" conveys authority. The rulers referred to are fallen angels, who are ruled by Satan, the "prince of the power of the air".

The verse means that believers should be constantly on guard and prepared with God's armor, as they will not be as successful in spiritual battle without it. The "evil day" can refer to any moment of spiritual attack.