Be strong; or, strengthen yourselves; i.e. be courageous, and constant in the practice of your duty, against the devil and all his assaults.
In the Lord: not in yourselves, but in the Lord Jesus Christ, in whom your strength lies, and from whom by faith you may obtain it: see Phi_4:132Ti_2:1.
And in the power of his might; or mighty power, see Eph_1:19: q.d. Though your own strength be but weakness, yet Christ’s power is mighty, and he can communicate enough to you.