3 John 1:3

The truth of Gaius's life was seen in the perfection of his works. He was a man who went about without any guile in thought, word or deed. Instead of that, he followed the commandments of God to the best of his ability.

I rejoiced greatly when the brothers came and bore witness to your truth, as you walk in the truth.
"you walk in the truth." He walks in truth who walks in the righteous simplicity of the Gospel. However, to walk does not refer to the motion of limbs, since such steps, passing from one place to another, are common to all animals that have feet; but it signifies an ordered and measured progress according to the keen affection of the mind, which few attain, even among those who are not lacking in understanding.

He who walks in the truth is one who walks according to the simplicity of the Gospel. By the word "walk" one must understand not the movement of feet, for such stepping motion from place to place is characteristic of every animal that has legs, but the orderly and sober progress in the strivings of the soul, which few achieve even among those who possess reason.