Finally. The apostle has now reached his last passage, and by this word quickens the attention of his readers and prepares them for a counsel eminently weighty in itself, and gathering up the pith and marrow, as it were, of what goes before.
"My brethren," A.V., is rejected by R.V, and most modern commentators, for lack of external evidence. We note, however, that, whereas in the preceding verses he had distributed the Ephesians into groups, giving an appropriate counsel to each, he now brings them again together, and has a concluding counsel for them all.
Be strong in the Lord, and in the power of his might. Compare with Ephesians 3:16, where the heavenly provision for obtaining strength is specified, and with Ephesians 4:30, where we are cautioned against a course that will fritter away that provision.
The ever-recurring formula, "in the Lord," indicates the relation to Christ in which alone the strength can be experienced. The might is Christ's, but by faith it becomes our strength. As the steam-engine genders the dynamic force, which belts and wheels communicate to the inert machinery of the factory, so Christ is the source of that spiritual strength which through faith is communicated to all his people.
To be strong is our duty; to be weak is our sin. Strong trust, strong courage, strong endurance, strong hope. strong love, may all be had from him, if only our fellowship with him be maintained in uninterrupted vigor.