Before Julian apostatized from the Christian faith, he was a young man of piety. Once he and his brother Gallus undertook to build a large edifice for the tomb and relics of Saint Mamas in Cappadocia. While the work of Gallus prospered, that of Julian kept coming to ruin, causing many to believing later on that this was an omen of the future actions of Julian, who instead of honoring the martyrs would one day make martyrs through the persecution he initiated. This story comes from two sources, namely Sozomen and Gregory the Theologian; the latter does not specifically name Mamas but instead the Martyrs in general, and likens the two brothers to Cain and Abel. Below are the two accounts of Sozomen and Gregory.
Sozomen
Ecclesiastical History (Bk. 5, Ch. 2)
[Julian] was born of pious parents, had been initiated in infancy according to the custom of the Church, and had been brought up in the knowledge of the Holy Scriptures, and was nurtured by bishops and men of the Church. He and Gallus were the sons of Constantius, the brother by the same father of Constantine the emperor, and of Dalmatius. Dalmatius had a son of the same name, who was declared Caesar, and was slain by the soldiery after the death of Constantine. His fate would have been shared by Gallus and Julian, who were then orphans, had not Gallus been spared on account of a disease under which he was laboring, and from which, it was supposed, that he would soon naturally die; and Julian, on account of his extreme youth, for he was but eight years of age. After this wonderful preservation, a residence was assigned to the two brothers in a palace called Macellum, situated in Cappadocia; this imperial post was near Mount Argeus, and not far from Caesarea; it contained a magnificent palace and was adorned with baths, gardens, and perennial fountains. Here they were cultured and educated in a manner corresponding to the dignity of their birth; they were taught the sciences and bodily exercises befitting their age, by masters of languages and interpreters of the Holy Scriptures, so that they were enrolled among the clergy, and read the ecclesiastical books to the people. Their habits and actions indicated no dereliction from piety. They respected the clergy and other good people and persons zealous for doctrine; they repaired regularly to church and rendered due homage to the tombs of the martyrs.
It is said that they undertook to deposit the tomb of Saint Mamas the Martyr in a large edifice, and to divide the labor between themselves, and that while they were trying to excel one another in a rivalry of honor, an event occurred which was so astonishing that it would indeed be utterly incredible were it not for the testimony of many who are still among us, who heard it from those who were eyewitnesses of the transaction.
The part of the edifice upon which Gallus labored advanced rapidly and according to wish, but of the section upon which Julian labored, a part fell into ruin; another was projected upward from the earth; a third immediately on its touching the foundation could not be held upright, but was hurled backward as if some resistant and strong force from beneath were pushing against it.
This was universally regarded as a prodigy. The people, however, drew no conclusion from it till subsequent events manifested its import. There were a few who from that moment doubted the reality of Julian's religion, and suspected that he only made an outward profession of piety for fear of displeasing the emperor, who was then a Christian, and that he concealed his own sentiments because it was not safe to divulge them. It is asserted that he was first secretly led to renounce the religion of his fathers by his intercourse with diviners; for when the resentment of Constantius against the two brothers was abated, Gallus went to Asia, and took up his residence in Ephesus, where the greater part of his property was situated; and Julian repaired to Constantinople, and frequented the schools, where his fine natural abilities and ready attainments in the sciences did not remain concealed.
Gregory the Theologian
Oration 4.23-29: First Invective Against Julian
Whilst [Julian and Gallus] were here enjoying complete leisure, imperial rank being still in the future, and being prepared for them, whilst their age and expectations did not yet exalt them to the secondary dignity; they had masters in all branches of learning, their uncle and sovereign causing them to be instructed in the complete and regular course of education; they studied also, and still more extensively, our own kind of philosophy, that which deals not with words alone, but which conveys piety by means of moral training: living in intercourse with the most excellent of men, and in the exercise of the most pleasant of occupations, and which offers a great field for the display of virtue: for both brothers offered and enrolled themselves amongst the clergy; reading aloud the sacred books to the people, thinking that this tended not a little to their glory, and that piety was a greater decoration than all things else.
By most sumptuous monuments to Martyrs, by emulation in their offerings, by all the other marks by which the fear of God is characterized, did they make known their love of wisdom and their love of Christ: the one of them being sincerely pious; for although too hasty in temper, nevertheless he was genuine in his piety: the other awaiting his opportunity, and concealing under a mask of goodness his evil disposition. A proof of this (for indeed I cannot omit noticing it) was the miracle which then occurred, one highly deserving of being remembered, and capable of opening the eyes of many of the ungodly.
Both the brothers were, as I have told you, laboring for the Martyrs, and were zealously vying with one another in erecting an edifice to their honor with a large and efficient body of workmen: but inasmuch as the work did not proceed from the same motive, so neither did the labor come to the same end with both: for the work of the one (the elder brother, I mean) was finishing, and going on according to calculation, as though God readily accepted the offering, like Abel's sacrifice, rightly offered up, and cut in pieces; for the donation was, in some sort, the consecration of the first-fruits of the flock: but the offering of the other (alas for the dishonor of the impious, that already in this world bears testimony to the next, and that proclaims beforehand great events by trifling signs!), the God of Martyrs rejected it, as He did the sacrifice of Cain!
And he continued laboring, and the earth shook off what he had toiled at, and he grew all the more zealous in the task, and she rejected the foundations of him that was unsound in the faith; as though she were crying aloud at the shaking of the world that was about to proceed from him, and doing honor to the Martyrs through the dishonor she did to the most impious of men. This fact was a kind of presage of the future obstinacy and madness of the man, and of his insults to the Martyrs, and of his lawless conduct against the sacred edifices -- one that from afar pursued the persecutor, and signified in advance the recompense of his impiety!
O thou Soul, clever truly for evil-doing, yet that canst not escape thy own punishment! O thou God, that hidest the future, in order that it may either cut short impiety, or display Thy foreknowledge! Oh unexpected, yet more true than unexpected miracle! Oh brotherly love of the Martyrs! They did not accept honor from him that was hereafter to do dishonor to many Martyrs; they did not receive the gift of him that was hereafter to make many Confessors, or rather, to begrudge them the credit of the conflict! Or, to speak more correctly, they did not suffer themselves to be the only Martyrs to be insulted, whilst the others were interred and cared for by pious Lands; nor would they give the Sophist of Wickedness the pleasure of exulting over the insults done them, in order that by the same hand some monuments of the Martyrs should be set up, and others pulled down; and that some Martyrs should be honored, but others dishonored; whilst the honor in semblance anticipated by but a little while the dishonor in reality; lest, in addition to the greatness of the insult, he should think in himself how clever he was in thus cheating (as he did man) God also----the most quick-sighted, the All Wise, He who "seizeth the wise in their craftiness"----by means of his outward show; but that he might know that he was understood, and that he might not be puffed up, seeing that he was detected.
For if the God of Martyrs had not checked his impiety, nor had dried up, like a poisonous stream, his intended and concealed villainy, or cut it short by what means He only knew, according to His hidden wisdom and government, like as He suffered the iniquities of the Amorites to fill up their measure; but it was needful that his evil intention should be hated, and his offering be rejected, for the edification of the multitude, and that the justice and purity of God with respect to the things offered unto Himself should be manifested to the world.
For He that said unto backsliding Israel, "If ye offer a wheaten cake, it is vain: your incense is an abomination unto me;" not accepting their New Moons and Sabbaths and Great Day, seeing that He, being full, stands not in need of anything that is human and little, so that He should take pleasure in those who offer to Him unworthily; for He abominates the sacrifice of transgressors, even though, it be a calf, as that of a dog, and their frankincense like a blasphemy; and excluding from the Temple and shaking off as defilement the hire of a harlot; whilst He gives honor to that sacrifice alone which pure hands bring unto the Most Pure, and a high and sanctified spirit. What wonder, then, if He did not accept honor from that man, offered in bad manner and from a bad motive, -- He that seeth not as man seeth, nor looketh at the outward appearance, but at the hidden man, and the inward workshop of virtue or of wickedness! So much for this; and if anyone is incredulous, we call in evidence those that beheld the fact, for they are numerous, who have delivered down the miracle to us, and will deliver it down to those who come after.