The Apostles were the mirror of Christianity. By word they explained it, and by life they presented it in deed. For a believer, to imitate them is the same duty as being faithful to the faith in all things. In ordinary life also, when someone first establishes certain customs, everyone imitates him. Such imitation passes from generation to generation.
“How you ought to imitate us.” How pure the apostolic conscience was! How blamelessly they acted in everything, according to the whole requirement of the Christian spirit! Living openly, before the eyes of all, they could say: live this way. They were certain that so many eyes could see nothing blameworthy in them. This was because they saw themselves as pure before the eyes of God, for they never consciously and willfully inclined toward anything about which conscience testified that it was contrary to the will of God. This mutual certainty gave them boldness to speak so. They were wholly sacrificed to God and by God, and they spoke so, moved by the Spirit, as men sacrificed to God in all things.
Saint Chrysostom writes: “Great boldness is given to a teacher by the thought that he can exhort his disciples by referring to his own righteous deeds. Therefore Paul also said, ‘You yourselves know how you ought to imitate us.’ For a teacher must teach more by life than by word. Let no one think that the Apostle said this from a desire to praise himself excessively. Necessity compelled him to say it, and moreover for the common benefit.”
Then, from the general sum of his deeds worthy of imitation, the Apostle fixes attention only on those which, by contrast with the faulty conduct of some Thessalonians, sternly exposed their fault. “We did not behave disorderly,” he says, “nor did we eat anyone’s bread for nothing.” He denies in himself the blameworthy traits of those being rebuked. Therefore, they acted disorderly and ate bread for nothing. But this ought not to have happened, just as it did not happen among the Apostles.
“We did not behave disorderly,” from the Greek οὐκ ἠτακτήσαμεν, means, “we did not live tactlessly.” Therefore those being rebuked lived tactlessly, without regard to time, place, or persons. Or they lived in disorder, since τάξις means order. That is, they did not live according to the orders to which their calling bound them, for example, as husband, father of a family, and the like. They lived carelessly, in idleness, wandering aimlessly through squares and markets, giving themselves over to popular amusements, revelry, and a carefree life. “By disorderliness here the Apostle means being without toil and work, as above. For God appointed man to be in labor, and for this reason furnished him with members fit for it. Therefore whoever remains idle steps out of God’s order” (Theophylact).