Charles Hodge on Ephesians 6:10

V. 10. Though the redemption purchased by Christ, as described in this epistle, is so complete and so free, yet between the beginning and the consummation of the work there is a protracted conflict. This is not a figure of speech. It is something real and arduous. Salvation, however gratuitous, is not to be obtained without great effort. The Christian conflict is not only real, it is difficult and dangerous. It is one in which true believers are often grievously wounded; and multitudes of reputed believers entirely succumb. It is one also in which great mistakes are often committed and serious loss incurred from ignorance of its nature, and of the appropriate means for carrying it on. Men are apt to regard it as a mere moral conflict between reason and conscience on the one side, and evil passions on the other. They therefore rely on their own strength, and upon the resources of nature for success. Against these mistakes the apostle warns his readers. He teaches that every thing pertaining to it is supernatural. The source of strength is not in nature. The conflict is not between the good and bad principles of our nature. He shows that we belong to a spiritual, as well as to a natural world, and are engaged in a combat in which the higher powers of the universe are involved; and that this conflict, on the issue of which our salvation depends, is not to be carried on with straws picked up by the wayside. As we have superhuman enemies to contend with, we need not only superhuman strength, but divine armour and arms. The weapons of our warfare are not natural, but divine.

Finally, my brethren, be strong in the Lord, τὸ λοιπὸν, ἀδελφοί μου, ἐνδυναμοῦσθε ἐν Κυρίῳ. He concludes his epistle so full of elevated views, and so rich in disclosures of the mysteries of redemption, with directions as to the struggle necessary to secure salvation. His first exhortation is to muster strength for the inevitable conflict, and to seek that strength from the right source. We are to be strong in the Lord. As a branch separated from the vine, or as a limb severed from the body, so is a Christian separated from Christ. He, therefore, who rushes into this conflict without thinking of Christ, without putting his trust in him, and without continually looking to him for strength and regarding himself as a member of his body, deriving all life and vigour from him, is demented. He knows not what he is doing. He has not strength even to reach the field. With him the whole conflict is a sham. The words καὶ ἐν τῷ κράτει τῆς ἰσχύος αὐτοῦ mean, in the vigour derived from his strength. The vigour of a man’s arm is derived from the strength of his body. It is only as members of Christ’s body that we have either life or power. It is not we that live, but Christ that liveth in us; and the strength which we have is not our own but his. When we are weak, then are we strong. When most empty of self, we are most full of God.