By the word of truth, by the power of God, by the armour of righteousness on the right hand and on the left, By the word of truth - The doctrine of truth received immediately from God, and faithfully and affectionately preached to men.
By the power of God - Confirming this doctrine, not only by the miracles which we were enabled to work, but also by the application of that truth to the souls of the people by the energy of God.
By the armor of righteousness - Such as that described by the apostle, Ephesians 6:13-17, which he calls there the whole armor of God, consisting of the following pieces: the girdle of truth, the breastplate of righteousness, the shoes of the Gospel of peace, the shield of faith, the helmet of salvation, and the sword of the Spirit.
On the right hand and on the left - Particularly, the shield and the sword; the former on the left arm, the latter in the right hand. We have the doctrine of truth, and the power of God, as an armor to protect us on all sides, every where, and on all occasions.
It seems far-fetched to understand the right hand as signifying prosperity, and the left as signifying adversity; as if the apostle had said: We have this armor to defend us both in prosperity and adversity. By the doctrine of the Gospel, and by the power of God, the apostles were furnished with offensive and defensive weapons; they could ever defend themselves, and discomfit their foes.