Grammar for the win

This morning we heard an excellent sermon from Ephesians 6.  But the part of the sermon I keep ruminating over is a point of grammar.  Verse 10 of that chapter says:

"Finally, be strong in the Lord and in the strength of his might."

In this verse, the command to "be strong" is actually in the passive voice.  For those of you who have taken composition with me, you know what that means.  It means that the action is not being done by the subject, but being done to the subject.  I sometimes call the passive the voice of victimhood to help my fledglings remember that in passive voice the subject is the victim of the verb.  So, according to my learned pastor, instead of a straight command to do something here, to "be strong," the sense of this verse is more along the lines of "Be kept strong."

Now that may seem like a superfluous difference of trivial semantics to you, Gentle Reader, a mere trifling with words.  But the difference here is huge.  If this verb is active, I am left in sheer exhaustion of resources.  How can I be strong in and of myself when the slings and arrows come my way?  But if I am to be kept strong, ah, then I can sink into the arms of Christ, and trust Him to keep me in perfect peace. I am a victim of His grace and protection. And that is a huge difference.

Grammar: it is not just for English teachers. It makes theologians of us all.