How then, one may say, are James and the others called His brethren? In the same kind of way as Joseph himself was supposed to be husband of Mary. For many were the veils provided, that the birth, being such as it was, might be for a time screened. Wherefore even John so called them, saying, For neither did His brethren believe in Him.
Nevertheless they, who did not believe at first, became afterwards admirable, and illustrious. At least when Paul and they that were of his company had come up to Jerusalem about decrees, they went in straightway unto James. For he was so admired as even to be the first to be entrusted with the bishop’s office. And they say he gave himself up to such great austerity, that even his members became all of them as dead, and that from his continual praying, and his perpetual intercourse with the ground, his forehead became so callous as to be in no better state than a camel’s knees, simply by reason of his striking it so against the earth. This man gives directions to Paul himself, when he was after this come up again to Jerusalem, saying, You see, brother, how many thousands there are of them that have come together. So great was his understanding and his zeal, or rather so great the power of Christ. For they that mock Him when living, after His death are so filled with awe, as even to die for Him with exceeding readiness. Such things most of all show the power of His resurrection. For this, you see, was the reason of the more glorious things being kept till afterwards, viz. that this proof might become indisputable. For seeing that even those who are admired among us in their life, when they are gone, are apt to be forgotten by us; how was it that they, who made light of this Man living, afterwards thought Him to be God, if He was but one of the many? How was it that they consented even to be slain for His sake, unless they received His resurrection on clear proof?
Homilies on Matthew
Homily 5; Matthew 1:22-23