Stand firm then, with the belt of truth buckled around your waist, with the breastplate of righteousness in place, and with your feet fitted with the readiness that comes from the gospel of peace. In addition to all this, take up the shield of faith, with which you can extinguish all the flaming arrows of the evil one. Take the helmet of salvation and the sword of the Spirit, which is the word of God.Ephesians 6:14-17 NIV
This third piece of armor is the gospel of peace. And Paul identifies this with our feet. The Roman soldier wore heavy sandals with good tread. It gave them good traction when fighting. But they also enabled them to travel long distances. Their sandals allowed them to take the fight to the enemy rather than waiting for them to attack.
In the Great Commission in Matthew 28:18-20 Jesus commissions his church to take the gospel with them, wherever they go. Whenever they go. In order to go, you need good sandals, or shoes. And when you go, take the gospel.
All too often we are content to sit in our secure sanctuaries, safe from the devil in the company of other sequestered believers. And we are content to let the enemy ravage the world around us. Just so long as he leaves us alone.
But Jesus said to go. And Paul here tells us to strap on our shoes, the shoes of the gospel message. Take the battle to the enemy. And do it, not with human weapons. But with the gospel of peace. The good news that God loves us and has provided a redeemer for us.