42 And whosoever shall offend one of these little ones that believe in me, it is better for him that a millstone were hanged about his neck, and he were cast into the sea.
[AD 430] Augustine of Hippo on Mark 9:38-42
(de Con. Evan. 4. 5.) We must take care that this saying of the Lord appear not to be contrary to that, where He says, He who is not with me is against me. (Luke 11:23) Or will any one say that the difference lies in that here He says to His disciples, For he that is not against you is on your part, but in the other He speaks of Himself, He who is not with me is against me? As if indeed it were possiblel that he who is joined to Christ's disciples, who are as His members, should not be with Him. How if it were so, could it be true that he that receiveth you receiveth me? (Matt. 10:40) Or how is he not against Him, who is against His disciples? Where then will be that saying, He who despiseth you, despiseth me? But surely what is implied is, that a man is not with Him in as far as he is against Him, and is not against Him in as far as he is with Him. For instance, he who worked miracles in the name of Christ, and yet did not join himself to the body of His disciples, in as far as he worked the miracles in His name, was with them, and was not against them: again, in that he did not join their society, he was not with them, and was against them. But because they forbade his doing that in which he was with them, the Lord said unto them, Forbid him not; for they ought to have forbidden his being without their society, and thus to have persuaded him of the unity of the Church, but they should not have forbidden that in which he was with them, that is, his commendation of the name of their Lord and Master by the expulsion of devils. Thus the Church Catholic does not disapprove in heretics the sacraments, which are common, but she blames their division, or some opinion of theirs adverse to peace and to truth; for in this they are against us.

(de Con. Evan. 4. 6) By which He shows, that he of whom John had spoken was not so far separated from the fellowship of the disciples, as to reject it, as a heretic, but as men are wont to hang back from receiving the Sacraments of Christ, and yet favour the Christian name, so as even to succour Christians, and do them service only because they are Christians. Of these He says they shall not lose their reward; not that they ought already to think themselves secure on account of this good will which they have towards Christians, without being washed with His baptism, and incorporated in His unity, but that they are already so guided by the mercy of God, as also to attain to these, and thus to go away from this life in security.

[AD 604] Gregory the Dialogist on Mark 9:38-42
(in Ezech. 1. Hom. 7) We must observe, however, that in our good works we must sometimes avoid the offence of our neighbour, sometimes look down upon it as of no moment. For in as far as we can do it without sin, we ought to avoid the offence of our neighbour; but if a stumblingblock is laid before men in what concerns the truth, it is better to allow the offence to arise, than that the truth should be abandoned.

(de cura past. p. i. c. 2) Mystically by a millstone is expressed the tedious round and toil of a secular life, and by the depths of the sea, the worst damnation is pointed out. He who therefore, after having been brought to a profession of sanctity, destroys others, either by word or example, it had been indeed better for him that his worldly deeds should render him liable to death, under a secular garb, than that his holy office should hold him out as an example for others in his faults, because doubtless if he had fallen alone, his pain in hell would have been of a more endurable kind.

[AD 735] Bede on Mark 9:38-42
(ubi sup.) John, loving the Lord with eminent devotion, thought that He who performed an office to which He had no right was to be excluded from the benefit of it. Wherefore it is said, And John answered him, saying, Master, we saw one casting out devils in thy name, and he followeth not us: and we forbad him, because he followeth not us.

(ubi sup.) By which He shows that no one is to be driven away from that partial goodness which he possesses already, but rather to be stirred up to that which he has not as yet obtained.

(ubi sup.) And fitly the man who is offended is called a little one, for he who is great, whatever he may suffer, departs not from the faith; but he who is little and weak in mind looks out for occasions of stumbling. For this reason we must most of all look to those who are little ones in the faith, lest by our fault they should be offended, and go back from the faith, and fall away from salvation.

[AD 1107] Theophylact of Ohrid on Mark 9:38-42
Or again, some unbelievers, seeing that the name of Jesus was full of virtue, themselves used it, and performed signs, though they were unworthy of Divine grace; for the Lord wished to extend His name even by the unworthy.

For how can he speak evil of Me, who draws glory from My name, and works miracles by the invocation of this very name. There follows, For he that is not against you is on your part.

Not only will I not forbid him who works miracles in My name, but also whosoever shall give you the smallest thing for My name's sake, and shall receive you, not on account of human and worldly favour, but from love to Me, shall not lose his reward.

[AD 1274] Pseudo-Chrysostom on Mark 9:38-42
(Vict. Ant. e Cat. in Marc.) For many believers received gifts, and yet were, not with Christ, such was this man who cast out devils; for there were many of them deficient in some way; some were pure in life, but were not so perfect in faith; others again, contrariwise.

(Vict. Ant. e Cat. in Marc.) It was not from jealousy or envy, however, that John wished to forbid him who cast out devils, but because he wished that all, who called on the name of the Lord, should follow Christ, and be one body with His disciples. But the Lord, however unworthy they who perform the miracles may be, incites others by their means to believe on Him, and induces themselves by this unspeakable grace to become better. Wherefore there follows: But Jesus said, Forbid him not.

(Vict. Ant. e Cat. in Marc.) In conformity to this, He shows that he is not to be forbidden, adding immediately after, For there is no man which shall do a miracle in my name, that can lightly speak evil of me. He says lightly, to meet the case of those who fell into heresy, such as were Simon and Menander, and Cerinthusk; not that they did miracles in the name of Christ, but by their deceptions had the appearance of doing them. But these others, though they do not follow us, cannot however set themselves to say any thing against us, because they honour My name by working miracles.

(Vict. Ant. e Cat. in Marc.) Or else, this is said of those who believe on Him, but nevertheless do not follow Him from the looseness of their lives. Again, it is said of devils, who try to separate all from God, and to disperse His congregation. There follows, For whosoever shall give you a cup of cold water to drink in my name, because ye belong to Christ, verily I say unto you, he shall not lose his reward.

(Vict. Ant. e Cat. in Marc.) And that no man may allege poverty, He mentions that, of which none can be destitute, that is, a cup of cold water, for which also he will obtain a reward; for it is not the value of the gift, but the dignity of those who receive it, and the feelings of the giver, which makes a work worthy of reward. His words show that His disciples are to be received, not only on account of the reward, which he who receives them obtains, but also, because he thus saves himself from punishment. There follows: And whosoever shall offend one of these little ones that believe in me, it is better for him that a millstone were hanged about his neck, and he were cast into the sea: as though He would say,1 All who honour you for My sake have their reward, so also those who dishonour you, that is, offend you, shall receive the worst of vengeance. Further, from things which are palpable to us, He describes an intolerable torment, making mention of a millstone, and of being drowned; and He says not, let a millstone be hanged about his neck, but, it is better for him to suffer this, showing by this that some more heavy evil awaits him. But He means by little ones that believe on Me, not only those who follow Him, but those who call upon His name, those also who offer a cup of cold water, though they do not any greater works. Now He will have none of these offended or plucked away; for this is what is meant by forbidding them to call upon His name.

[AD 99] Clement of Rome on Mark 9:42
Remember the words of our Lord Jesus Christ, how He said, "Woe to that man [by whom offenses come]! It were better for him that he had never been born, than that he should cast a stumbling-block before one of my elect. Yea, it were better for him that a millstone should be hung about [his neck], and he should be sunk in the depths of the sea, than that he should cast a stumbling-block before one of my little ones." Your schism has subverted [the faith of] many, has discouraged many, has given rise to doubt in many, and has caused grief to us all. And still your sedition continues.

[AD 430] Augustine of Hippo on Mark 9:42
He did not shrink from using the same words three times over in one passage. And who is not terrified by this repetition and by the threat of that punishment uttered so vehemently by the lips of the Lord himself?

[AD 604] Gregory the Dialogist on Mark 9:42
In Faeceh., 1, Hom. 7: We must observe, however, that in our good works we must sometimes avoid the offence ofour neighbour, sometimes look down upon it as of no moment. For in as far as wecan do it without sin, we ought to avoid the offence of our neighbour; but if astumblingblock is laid before men in what concerns the truth, it is better toallow the offence to arise, than that the truth should be abandoned.
de eura, past. p.i.v.2: Mystically by a millstone is expressed the tedious round and toil of a secular life, and by the depths of the sea, the worst damnation is pointed out. He who therefore, after having been brought to a profession of sanctity, destroys others, either by word or example, it had been indeed better for him that his worldly deeds should render him liable to death, under a secular garb, than that his holy office should hole him out as an example for others in his faults, because doubtless if he had fallen alone, his pain in hell would have been of a more endurable kind.
[AD 735] Bede on Mark 9:42
And whoever shall cause one of these little ones who believe in me to stumble, it would be better for him if a heavy millstone were hung around his neck, and he were cast into the sea. Although this general sentence can be applied against all who cause someone to stumble, yet according to the context of the speech, it can also be understood as said against the apostles, who, disputing among themselves over who was the greatest, seemed to be contending over dignity with each other. And if they had remained in this vice, they could lose those whom they called to faith through their scandal, while seeing the apostles fighting among themselves over honor. What he said: It is better for him if a millstone were hung around his neck, speaks according to the custom of the province, where among the ancient Jews the punishment for greater crimes was that they were drowned in the deep with a stone tied around them. And indeed it is better for an innocent person, however atrocious the temporal punishment, to end his bodily life, than by harming a brother, to deserve eternal death of the soul. And rightly, someone who can be scandalized is called little. For whoever is great, whatever he may see, whatever he may suffer, he does not depart from the faith. But whoever is little in mind and small, he seeks occasions to be scandalized. Therefore it is necessary for us especially to take care of those who are small in faith, lest by our occasion they are offended and withdraw from the faith, and fall from salvation. It is to be noted certainly, that in our good work, sometimes the scandal of our neighbor must be avoided: but sometimes it is to be utterly disregarded. For in as much as we can avoid the scandal of our neighbors without sin, we ought to. But if scandal arises from the truth, it is more useful to permit scandal to arise, than to abandon the truth. Also, by the millstone, the circular and laborious nature of secular life is expressed, and by the depth of the sea, final damnation is designated. Therefore, whoever has been brought to the appearance of holiness, or destroys others by word or example; truly, it was better for this person to be bound to earthly deeds under an outward appearance until death, than to demonstrate to others the sacred duties in fault as something to imitate. For certainly if he alone fell, somehow the more tolerable punishment of hell would torture him.