Verse explainer
The command isn't 'try harder' — it's 'draw your strength from the Lord, not from yourself.'
Finally, my brethren, be strong in the Lord, and in the power of his might.
BSBFinally, be strong in the Lord and in His mighty power.
The plain meaning
Paul has spent six chapters laying out what the Christian life looks like — in doctrine, in households, in relationships. Now he turns to the fight. 'Finally' (or, in some manuscripts, 'henceforward') signals that everything before this is the reason you'll need what comes next. The command is 'be strong' — but the grammar is passive: be strengthened. The source is 'the Lord,' and the fuel is 'the power of his might,' the same phrase Paul used in Ephesians 1:19 to describe the force that raised Christ from the dead. That's not motivational language; it's a theological claim about where the resource comes from. Verses 11–18 unpack what this looks like practically — the full armor. But v. 10 is the hinge: no armor works if the soldier is drawing on his own reserves. The whole armor passage collapses without this foundation. The enemies Paul names in v. 12 are not human opponents but 'principalities and powers' — which means human willpower and discipline, however admirable, are simply the wrong category of weapon.
The common misreading
What the commentators say
Henry reads this verse as the essential pre-condition for everything that follows: a soldier must be stout-hearted before armor does any good. He stresses that our natural courage is 'as perfect cowardice' and our natural strength 'as perfect weakness' — all sufficiency must come from God. The way to access that strength, he says, is through active faith: drawing on heaven's omnipotence by trusting it, not by generating more effort from within.
Clarke sees v. 10 as the transition point of the entire letter: having laid out the calling and the doctrines, Paul now shows what enemies stand against them and what kind of strength repels those enemies. The strength required is specifically spiritual, and specifically Christ's — communicated through an indwelling God, 'the power of his might working in you.' Clarke's emphasis is that the strength is real and available, but it is not the believer's own.
Gill notes the tender address 'my brethren' — Paul speaks as a fellow soldier, not a distant commander — and then focuses on what 'be strong in the Lord' actually means practically: meditation on Christ's strength, prayer for it, waiting on him, and above all exercising faith toward him. Weakness in oneself is assumed and acknowledged; the point is that strength in Christ is real, communicable, and accessible.
The word behind it
'Be strengthened' — a present passive imperative from endunamoō, meaning to be made powerful from within. The passive voice is the theological weight: the believer is not the agent generating strength but the one receiving it. The same root appears in Philippians 4:13 ('I can do all things through Christ who strengthens me'). Jamieson-Fausset-Brown note this explicitly: the Greek is not 'be strong' as an act of will but 'be strengthened' as an act of reception.
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