“Therefore, since Christ suffered for us in the flesh, arm yourselves also with the same mind, for he who has suffered in the flesh has ceased from sin.”
“Arm” means to put on armor with the same care as a soldier. This is the only occurrence of the Greek word in the New Testament. “Arm” was used of a Greek soldier taking up his heavy weapons for war. The noun was used for a soldier who was heavily armed with javelin and large shield. The main idea is that this soldier is heavily armed.
Since Christ found it necessary to go to the cross and suffer because of our sin, we should develop the same kind of thinking. God wants us to significantly arm our minds with the same mind that Jesus had in the way he approached undeserved suffering.
There is a suffering that comes from breaking off from the fast crowd (4:1-6). The old friends will not take it lightly that you no longer run with them. This is a form of undeserved suffering.
To be forewarned is to be forearmed.
Are you ready for spiritual battle? Have your armed yourself with the implements of spiritual war? Have you fitted yourself as a spiritual soldier with heavy armor? We need to become as heavily armed as we can to fight a spiritual war. We need to deal decisively with sin.
As we bring the Word of God into the battle with sin, the Word changes our thinking about sin (Ps. 119:9,11). If we appropriate the Word to our lives the influence of that fast crowd weakens. The influence of our peers weakens against the power of the Word.
Every time we resist temptation we become stronger to resist the next temptation. Each time we conquer sin this makes us better able to face the next attack. As we build a momentum of conquering sin we become more spiritually mature. Spiritual maturity guarantees infrequency of sin in our lives.