On Eutropia in Eusebius, Vitae Constantini
LI. That he ordered a Church to be built at Mambre.
Such was the principal sacred edifices erected by the emperor's command. But having heard that the self-same Saviour who erewhile had appeared on earth had in ages long since past afforded a manifestation of his Divine presence to holy men of Palestine near the oak of Mambre, he ordered that a house of prayer should be built there also in honor of the God who had thus appeared. Accordingly the imperial commission was transmitted to the provincial governors by letters addressed to them individually, enjoining a speedy completion of the appointed work. He sent moreover to the writer of this history an eloquent admonition, a copy of which I think it well to insert in the present work, in order to convey a just idea of his pious diligence and zeal. To express, then, his displeasure at the evil practices which he had heard were usual in the place just referred to, he addressed me in the following terms.
LII. Constantine's Letter to Eusebius concerning Mambre.
"Victor Constantinus, Maximus Augustus, to Macarius, and the rest of the bishops in Palestine. "One benefit, and that of no ordinary importance, has been conferred on us by my truly pious mother-in-law, in that she has made known to us by letter that abandoned folly of impious men which has hitherto escaped detection by you: so that the criminal conduct thus overlooked may now through our means obtain fitting correction and remedy, necessary though ardy. For surely it is a grave impiety indeed, that holy places should be defiled by the stain of unhallowed impurities. What then is this, dearest brethren, which, though it has eluded your sagacity, she of whom I speak was impelled by a pious sense of duty to disclose?
LIII. That the Saviour appeared in this Place to Abraham.
"She assures me, then, that the place which takes its name from the oak of Mambre, where we find that Abraham dwelt, is defiled by certain of the slaves of superstition in every possible way. She declares that idols which should be utterly destroyed have been erected on the site of that tree; that an altar is near the spot; and that impure sacrifices are continually performed. Now since it is evident that these practices are equally inconsistent with the character of our times, and unworthy the sanctity of the place itself, I wish your Gravities to be informed that the illustrious Count Acacius, our friend, has received instructions by letter from me, to the effect that every idol which shall be found in the place above-mentioned shall immediately be consigned to the flames; that the altar be utterly demolished; and that if any one, after this our mandate, shall be guilty of impiety of any kind in this place, he shall be visited with condign punishment. The place itself we have directed to be adorned with an unpolluted structure, I mean a church; in order that it may become a fitting place of assembly for holy men. Meantime, should any breach of these our commands occur, it should be made known to our clemency without the least delay by letters from you, that we may direct the person detected to be dealt with, as a transgressor of the law, in the severest manner. For you are not ignorant that the Supreme God first appeared to Abraham, and conversed with him, in that place. There it was that the observance of the Divine law first began; there first the Saviour himself, with the two angels, vouchsafed to Abraham a manifestation of his presence; there God first appeared to men; there he gave promise to Abraham concerning his future seed, and straightway fulfilled that promise; there he foretold that he should be the father of a multitude of nations.
For these reasons, it seems to me right that this place should not only be kept pure through your diligence from all defilement, but restored also to its pristine sanctity; that nothing hereafter may be done there except the performance of fitting service to him who is the Almighty God, and our Saviour, and Lord of all. And this service it is incumbent on you to care for with due attention, if your Gravities be willing (and of this I feel confident) to gratify my wishes, which are especially interested in the worship of God. May he preserve you, beloved brethren!"
Eusebius, Vitae Constantini (book III, chaps 51-53).