1 Thessalonians 3:10

But to those who are still babes in mind, and who as carnal, the apostle says, require to be nourished with milk, all discoursing on such a subject, wherein we deal not only with the believing, but also with the understanding and the knowing of what is spoken, must be burdensome, as being still unable to perceive such things, and be more fitted to oppress than to feed them. Whence it comes to pass that the spiritual, while not altogether silent on such subjects to the carnal, because of the Catholic faith which is to be preached to all, yet do not so handle them as, in their wish to simplify them to understandings that are still deficient in capacity, to bring their discourse on the truth into disrepute, rather than the truth that is in their discourse within the perceptions of their hearers. Accordingly in his Epistle to the Colossians he says: "And though I be absent in the flesh, yet am I with you in the spirit, joying and beholding your order, and that which is lacking in your faith in Christ." And in that to the Thessalonians: "Night and day," he says, "praying more abundantly, that we might see your face, and might perfect that which is lacking in your faith."

And let not the admonition of the most blessed apostle by any means lose its place in your hearts: "If any man preach any other gospel unto you than that ye have received, let him be accursed." He does not say, More than ye have received; but, "Other than ye have received." For had he said the former, he would be prejudging himself, inasmuch as he desired to come to the Thessalonians to supply what was lacking in their faith. But one who supplies, adds to what was deficient, without taking away what existed: while he that transgresses the rule of faith, is not progressing in the way, but turning aside from it.

"For what thanksgiving can we render again unto God for you, for all the joy wherewith we joy for your sakes before our God; night and day praying exceedingly that we may see your face, and may perfect that which is lacking in your faith?" Not only, he says, are ye the causes of life to us, but also of much joy, and so much that we cannot worthily give thanks to God. Your good behavior, he says, we consider to be the gift of God. Such kindnesses have you shown to us, that we think it to be of God; yea, rather, and it is of God. For such a disposition of mind comes not of a human soul or carefulness. "Night and day," he says, "praying exceedingly." This too is a sign of joy. For as any husbandman, hearing concerning his land that has been tilled by himself, that it is burdened with ears of grain, longs with his own eyes to see so pleasant a sight, so Paul to see Macedonia. "Praying exceedingly." Observe the excess; "that we may see your face, and may perfect that which is lacking in your faith." Here there is a great question. For if now thou livest, because they stand fast, and Timothy brought thee "glad tidings of their faith and love," and thou art full of so much joy as not to be able worthily to give thanks to God, how sayest thou here that there are deficiencies in their faith? Were those then the words of flattery? By no means, far be it. For previously he testified that they endured many conflicts, and were no worse affected than the Churches in Judaea. What then is it? They had not enjoyed the full benefit of his teaching, nor learned all that it behoved them to learn. And this he shows toward the end. Perhaps there had been questionings among them concerning the Resurrection, and there were many who troubled them, not by temptations, nor by dangers, but by acting the part of teachers. […]

Note the intensification in the expression! "Praying most earnestly" to see them, just as a farmer, hearing that the field he cultivates abounds with fruit, impatiently desires to see it with his own eyes.

If above he testified to their "standing," then how does he now say: "what was lacking in your faith"? They did not benefit from all the teaching, and they were lacking, perhaps, knowledge about the resurrection and other similar matters. Also, there were many false …