Mark 9:31

But they understood not the word. That is to say, in what manner, and for what cause, Christ was to die; and how these words concerning His near approaching death agreed with what He had often told them, that His kingdom was at hand. For otherwise the Apostles understood and believed that Christ would die (see Mat 17:23), when they are said to have been sorry at this saying of Christ concerning His death. Unless you prefer to say that they were ignorant of the death of Christ, because they were in hesitation with respect to it on account of the different sayings of Christ, apparently inconsistent with one another, and that accordingly they inclined to the view which was the more pleasing to them. For it was this which they wished to be true. "For so lovers frame dreams for themselves." So they endeavoured to persuade themselves that these words of Christ concerning His death had some other hidden meaning, and that they were not to be taken literally, but mystically. Ver. 37. John answered Him, saying, Master, we saw one casting out devils in Thy name, who followeth not us, and we forbade him. It is as though he said, "Have we done well or ill?" John asks this question not out of envy, as Calvin would have it, but out of love and zeal for the honour of Christ. And it was occasioned by what He had said in the preceding verse, Whosoever shall receive one such little child in My name receiveth Me. As though he said, If he who receives a little one in Thy name receiveth Thy Father and Thyself, what must we think concerning him who works miracles in Thy name, and yet followeth not us, that is, is not Thy attendant and disciple, as we are? "Because," says Cyril (in Catena in Luke 11:49), "the Saviour had given power to His Apostles to cast out unclean spirits, they thought that it had been conceded to none others save themselves to enjoy such dignity." So Theophylact and Victor.

Here observe that those who thus cast out devils in the name of Christ, and yet did not follow Him, were believers, but imperfect ones, forasmuch as they shrank from the rugged poverty and renunciation of their goods, such as was the lot of the Apostles. They shrank from following Christ in His evangelical labours and His persecutions. Still they have some faith in Christ, by virtue of which they cast out devils. So S. Ambrose (in Luke 11:49). And in so doing Christ wrought and co-operated with them, that His power and glory might be the more made manifest, which wrought such great things by means of those who were so imperfect, and, as it were, aliens.

Observe, in the next place, that the Apostles did not forbid such people through hatred, but out of zeal for Christ, as though they were detracting from the glory of Christ and His ordinance, according to chap. iii. 15, where Christ gives to His Apostles only the power of casting out devils. But this zeal of theirs was indiscreet, especially because they had rashly, without consulting Christ, forbidden them. And Christ showed them that this was so for a double reason. The first is what He brings forward in the next verse. In a similar manner, when Joshua saw Eldad and Medad prophesying, he wished to forbid them, as if they were detracting from the glory of Moses, in that they had not received the spirit of prophecy from Moses. But Moses checked him by saying, "Enviest thou for my sake? Would that all the people were prophets, and that the Lord would put His Spirit upon them!" (Num 11:29). This is the Spirit of Christ, the spirit of love and of the Holy Ghost, which makes large the heart, and envieth none, but rejoices in all good things, by whomsoever and in what way soever they are wrought (see 1 Corinthians 13.). Ver. 38. But Jesus said, Do not forbid him, for there is no man that doth a miracle in My name, and can soon (Gr. τάχα, i.e., easily) speak ill of Me. Do not hinder him in a good work, and one that honours Me; because even if he does not follow Me, yet he is doing the selfsame thing which you do, that is to say, he is celebrating My name, and he is making it known to men by casting out devils. Wherefore he does nothing that is against My name, but rather propagates and glorifies it. Ver. 39. For he that is not against you is for you. This man, therefore, is not your adversary, in that he does the same that you do. He stands on your side. He helps you; he does not oppose you. Ver. 40. For whosoever shall give you to drink a cup of water in My name, because you belong to Christ: Amen I say to you, he shall not lose his reward. This is Christ's further reason to show why the man must not be forbidden to cast out devils. It is as though Christ said, "If he who gives you a drink of water in My name, and for My sake, does well, and shall receive a reward from God, so likewise shall he who drives out devils in My name. For both the one and the other do a good work, and are profitable to their neighbours in regard and respect of Me. But the one confers so much the greater benefit than the other, by as much as the devil whom he drives out is more hurtful than the thirst which the other alleviates by a draught of water." So Theophylact.