John Chrysostom

After shaming them by the slavery, after alarming them by the rewards, and so exhorting them, he again rights them by calling the benefits to mind. For by these he shows that they were great evils from which they were freed, and that not by any labors of their own, and that things henceforth would be more manageable. Just as any one who has rescued a captive from a cruel tyrant, and advises him not to run away back to him, reminds him of his grievous thraldom; so does Paul set the evils passed away most emphatically before us, by giving thanks to God. For it was no human power that could set us free from all those evils, but, "thanks be to God," who was willing and able to do such great things. And he well says, "Ye have obeyed from the heart." Ye were neither forced nor pressed, but ye came over of your own accord, with willing mind. Now this is like one that praises and rebukes at once. For after having willingly come, and not having had any necessity to undergo, what allowance can you claim, or what excuse can you make, if you run away back to your former estate? Next that you may learn that it came not of your own willing temper only, but the whole of it of God's grace also, after saying, "Ye have obeyed from the heart," he adds, "that form of doctrine which was delivered you." For the obedience from the heart shows the free will. But the being delivered, hints the assistance from God. But what is the form of doctrine? It is living aright, and in conformity with the best conversation.