John 7:4

On this holy day, then (for there were several holy days; but it was called a holy day with the Jews, though it was not one day, but several), "His brethren" spoke to the Lord Christ. Understand the phrase, "His brethren," as you know it must be taken, for it is not a new thing you hear. The blood relations of the Virgin Mary used to be called the Lord's brethren. For it was of the usage of Scripture to call blood relations and all other near kindred by the term brethren, which is foreign to our usage, and not within our manner of speech. For who would call an uncle or a sister's son "brother"? Yet the Scripture calls relatives of this kind "brothers." For Abraham and Lot are called brothers, while Abraham was Lot's uncle. Laban and Jacob are called brothers, while Laban was Jacob's uncle. When, therefore, you hear of the Lord's brethren, consider them the blood relations of Mary, who did not a second time bear children. For, as in the sepulchre, where the Lord's body was laid, neither before nor after did any dead lie; so, likewise, Mary's womb, neither before nor after conceived anything mortal. We have said who the brethren were, let us hear what they said: "Pass over hence, and go into Judea, that thy disciples also may see thy work which thou doest." The Lord's works were not hid from the disciples, but to these men they were not apparent. They might have Christ for a kinsman, but through that very relationship they disdained to believe on Him. It is told us in the Gospel; for we dare not hold this as a mere opinion, you have just now heard it. They go on advising Him: "For no man doeth anything in secret, and he himself seeketh to be known openly: if thou do these things, show thyself to the world." And directly after it says: "For neither did His brethren believe in Him." Why did they not believe in Him? Because they sought human glory. […]

(Tr. xxviii. 3) When you hear of our Lord's brethren, you must understand the kindred of Mary, not her offspring after our Lord's birth. For as the body of our Lord once only lay in the sepulchre, and neither before, nor after that once; so could not the womb of Mary have possibly conceived any other mortal offspring. Our Lord's works did not escape His disciples, but they escaped His brethren; hence their suggestion, That Thy disciples may see the works that Thou doest. They speak according to the wisdom of the flesh, to the Word that was made flesh, and add, For there is no man that doeth any thing in secret, and he himself seeketh to be known openly. If Thou do these things, show Thyself to the world; as if to say, Thou doest miracles, do them in the eyes of the world, that the world may honour Thee. Their admonitions aim at procuring glory for Him; and this very thing, viz. aiming at human glory, proved that they did not believe in Him, as we next read, For neither did His brethren believe on Him. They were Christ's kindred, but they were on that very account above believing in Him.

And it is worth our while to admire their truth-loving disposition, how they are not ashamed to relate things which seem to bring disgrace upon their Teacher, but have been even more anxious to report these than other matters. For instance, the writer having passed by many signs and wonders and sermons, has sprung at once to this. For, saith he, "His brethren said unto Him, Depart hence, and go into Judaea, that Thy disciples also may see the works that Thou doest; for there is no man that doeth anything in secret, and he himself seeketh to be known openly. Show thyself to the world. For neither did His brethren believe in Him." What unbelief, saith some one, is here? They exhort Him to work miracles. It is great deed; for of unbelief come their words, and their insolence, and their unseasonable freedom of speech. For they thought, that owing to their relationship, it was lawful for them to address Him boldly. And their request seems forsooth to be that of friends, but the words were those of great maliciousness. For in this place they reproach Him with cowardice and vainglory: since to say, "no man doeth anything in secret," is the expression of persons charging Him with cowardice, and suspecting the things done by Him as being not really done; and to add, that "he seeketh to be known," was to accuse Him of vainglory. But observe, I pray you, the power of Christ. Of those who said these things, one became first Bishop of Jerusalem, the blessed James, of whom Paul saith, "Other of the Apostles saw I none, save James, the Lord's brother" (Gal. i. 19); and Judas also is said to have been a marvelous man. And yet these persons had been present also at Cana, when the wine was made, but as yet they profited nothing. Whence then had they so great unbelief? […]

(Hom. xlviii. 1, 2) It is striking to observe the great sincerity of the Evangelists; that they are not ashamed to mention things which appear to be to our Lord's disadvantage, but take particular care to tell us of them. It is a considerable reflexion on our Lord, that His brethren do not believe on Him. The beginning of their speech has a friendly appearance about it: but there is much bitterness in it, thus charging Him with the motives of fear and vain glory; No man, say they, doeth any thing in secret: this was reproaching Him tacitly with fear; and was an insinuation too that His miracles had not been real and solid ones. In what follows, And he himself seeketh to be known openly, they taunt Him with the love of glory.

What unbelief, saith some one, is here? They exhort Him to work miracles. It is great deed; for of unbelief come their words, and their insolence, and their unseasonable freedom of speech. For they thought, that owing to their relationship, it was lawful for them to address Him boldly. And their request seems forsooth to be that of friends, but the words were those of great maliciousness. For in this place they reproach Him with cowardice and vainglory: since to say, "no man doeth anything in secret," is the expression of persons charging Him with cowardice, and suspecting the things done by Him as being not really done; and to add, that "he seeketh to be known," was to accuse Him of vainglory.