If thou dost these things; that is, if thou aspirest to such greatness that all may applaud thee, direct towards thee the eyes of all. And they add, show thyself to the world, using the word world, as contrasted with the small number of persons among whom he was spending his time without honor. We might also draw from it another meaning. "If thou dost these things, that is, since thou art endued with so great power as to procure reputation for thyself by miracles, do not throw them away; for all that has been given to thee by God thou spendest here to no purpose, because there are none to bear thee testimony, or to hold thee in just estimation." Hence we perceive how great is the indolence of men in considering the works of God; for the relations of Christ would never have spoken in this manner, if they had not -- as it were -- trampled under foot the manifest proofs of his Divine power, which they ought to have beheld with the greatest admiration and reverence. What is here told us concerning Christ happens in daily experience, that the children of God suffer greater annoyance from their near relations than from strangers; for they are instruments of Satan which tempt, sometimes to ambition, and sometimes to avarice, those who desire to serve God purely and faithfully. But such Satans receive a vigorous repulse from Christ, who thus instructs us by his example, that we ought not to yield to the foolish wishes of brethren or relations. [1]

Footnotes

1 - "De nos parens."

For there is no man - The brethren of Jesus supposed that he was influenced as others are. As it is a common thing among men to seek popularity, so they supposed that he would also seek it; and as a great multitude would be assembled at Jerusalem at this feast, they supposed it would be a favorable time to make himself known. What follows shows that this was said, probably, not in sincerity, but in derision; and to the other sufferings of our Lord was to be added, what is so common to Christians, derision from his relatives and friends on account of his pretensions. If our Saviour was derided, we also may expect to be by our relatives; and, having his example, we should be content to bear it.
If thou do - It appears from this that they did not really believe that he performed miracles; or, if they did believe it, they did not suppose that he was the Christ. Yet it seems hardly credible that they could suppose that his miracles were real, and yet not admit that he was the Messiah. Besides, there is no evidence that these relatives had been present at any of his miracles, and all that they knew of them might have been from report. See the notes at Mark 3:21. On the word brethren in John 7:5, see the Matthew 13:55 note, and Galatians 1:19 note.

No man that doeth any thing in secret, etc. - They took it for granted that Christ was influenced by the same spirit which themselves felt; and that therefore he should use every opportunity of exhibiting himself to the public, that he might get into repute; and they hoped that a part of his honor would be reflected back upon themselves, as being his near relations. They seem to have said: "It is too little to employ thyself in working miracles in Galilee, in the country, and in small villages, among an ignorant and credulous people, from whom thou canst not get much credit: go to Jerusalem, the capital, and among the learned doctors, in the presence of the whole nation assembled at this feast, work thy miracles, and get thyself a name."

For there is no man that doeth anything in secret,.... For so they reckoned his doing miracles in such a corner of the land, and in so obscure a place as Galilee:
and he himself seeketh to be known openly; suggesting hereby, that Christ was an ambitious person, and sought popular applause, and honour and glory from men, when nothing was more foreign from him; see John 5:41.
If thou do these things; for they question whether the miracles he wrought were real; and suspected that they were deceptions of the sight, and delusions; or at least they questioned their being done by him; and rather thought that they were done by diabolical influence, by Beelzebub the prince of devils: but if they were real ones, they advise him, saying,
shew thyself to the world; or do these openly, and in the presence of the great men of the world; the princes of it, the rulers of the people, the chief priests and sanhedrim; and before all the males of Israel; who at this feast would come up from all parts of the land, and are for their multitude called the world: the reason of this their advice was, that if his miracles were real, and he was the person he would be thought to be, the doing of them before such, would gain him great credit and esteem; and if not, he might be detected by such numbers, and by men of such penetration as were among them.

If thou do these things. These brethren still were doubters. He differed so from their idea of the Christ that they could not understand him, and they hoped that at Jerusalem he would be made manifest. They afterwards became believers.

For no man doth any thing - Of this kind, in secret; but rather desireth to be of public use. If thou really dost these things - These miracles which are reported; show thyself to the world - To all men.