Ambrose of Milan : Abraham, ready to receive strangers, faithful towards God, devoted in ministering, quick in his service, saw the Trinity in a type; he added religious duty to hospitality, when beholding Three he worshipped One, and preserving the distinction of the Persons, yet addressed one Lord, he offered to Three the honour of his gift, while acknowledging one Power. It was not learning but grace which spoke in him, and he believed better what he had not learnt than we who have learnt. No one had falsified the representation of the truth, and so he sees Three, but worships the Unity. He brings forth three measures of fine meal, and slays one victim, considering that one sacrifice is sufficient, but a triple gift; one victim, an offering of three. — On the Decease of His Brother Satyrus Augustine of Hippo : God appeared again to Abraham at the oak of Mamre in three men, who it is not to be doubted were angels, although some think that one of them was Christ and assert that he was visible before he put on flesh. Now it belongs to the divine power and invisible, incorporeal and incommunicable nature, without changing itself at all, to appear even to mortals, not by what it is but by what is subject to it. And what is not subject to it? Yet if they try to establish that one of these three was Christ by the fact that although he saw three, he addressed the Lord in the singular, as it is written, "He lifted up his eyes and looked, and behold, three men stood in front of him. When he saw them, he ran from the tent door to meet them, and bowed himself to the earth and said, 'My lord, if I have found favor in your sight.' " Why do they not refer also to this, that when two of them came to destroy the Sodomites, while Abraham still spoke to one, calling him Lord and interceding that he would not destroy the righteous along with the wicked in Sodom, Lot received these two in such a way that he too in his conversation with them addressed the Lord in the singular? For after saying to them in the plural, "My lords, turn aside, I pray you, to your servant's house," yet it is afterward said, "So [the angels] seized him and his hand, [because] the Lord [was] merciful to him, and they brought him forth and set him outside the city. And when they had brought them forth, they said, 'Flee for your life; do not look back or stop anywhere in the valley; flee to the hills, lest you be consumed.' And Lot said to them, 'Oh, no, my lords; behold, your servant has found favor in your sight.…' " And then after these words the Lord also answered him in the singular, although he was in two angels, saying, "Behold, I grant you this favor.…" This makes it much more credible that Abraham in the three men and Lot in the two recognized the Lord, addressing him in the singular number, even when they were addressing men; for they received them as they did for no other reason than that they might minister human nourishment to them as men who needed it. Yet there was about them something so excellent that those who showed them hospitality as men could not doubt that God was in them as he was wont to be in the prophets and therefore sometimes addressed them in the plural, and sometimes God in them in the singular. But that they were angels the Scripture testifies, not only in this book of Genesis, in which these transactions are related, but also in the epistle to the Hebrews, where in praising hospitality it is said, "For thereby some have entertained angels unawares." — City of God 16.29 Bede : The Lord appeared to him in the valley of Mamre as he was sitting at the entrance of his tent in the heat of the day, etc. This appearance of the Lord is considered to be more sacred than all the previous ones, in which He was seen so many times by the blessed Abraham. And rightly so, after receiving the sacrament of circumcision, after the name was amplified by which he was to be marked as the father of all nations, he came to know the more secret mysteries of God, of which, notably, not only circumcision but also the uncircumcised were to be participants. Rightly, the appearance in the valley of Mamre is remembered as having taken place. For Mamre, as we read above, was indeed an Amorite by race, but together with his brothers, he was allied with Abraham; hence the valley of Mamre aptly represents our humility, who, having derived fleshly origin from the nations, have Abraham as our father in spirit and faith. To whom the Apostle, drawing from Abraham both the origin of flesh and virtue, says: We announce to you eternal life, which was with the Father and appeared to us; what we have seen and heard, we declare to you, so that you too may have fellowship with us (1 John 1:2). And indeed in this reading, apart from the spiritual understanding, it greatly edifies the readers that Abraham, seeing unknown men, immediately ran to meet them as if to offer the grace of hospitality to strangers; that he approached them humbly, worshipped on the ground, that he asked them to wait and accept his service, and hastily provided what they agreed to; and that he completed this not through servants and maidservants, but by himself and Sarah. It is indeed remarkable if, upon first seeing them, he did not believe they were men, why he would want to bring them water to wash their feet; how he would ask them to rest under a tree as if weary from walking; why he requested to strengthen their bodies with refreshment, as if they were laboring in fasting. If anyone seeks to investigate this reading more deeply, he will find it to be full of spiritual senses. For the fact that the Lord appeared to Abraham sitting at the entrance of his tent greatly suits both Abraham's devotion and that of all the heirs of the same promise, who testify that they are strangers and sojourners in this world but truly citizens of another life, that is, of the heavenly homeland. For we use tents in a journey or in war, but a house in our homeland, in which mystery, Isaac and Jacob are also read to have dwelled in tents. He who remains in the midst of his tent, knowing that he is a stranger and not destined to live forever in this world, and yet is not ashamed to engage himself as much as he can in the affairs and allurements of the world, remains. But Abraham and his followers, who conduct the things of the world out of necessity and not out of pleasure, sit as if at the entrance of their tent, because they are ready to leave the world at any moment, always with a joyful mind stretched towards the future rewards and waiting for the entrance into the following life. And it is well added, in the heat of the day; for the heat of the day, in which Abraham was sitting at the entrance of his tent, signifies the virtue of love with which he was burning in his mind with respect towards the Sun of righteousness. And such a state of place and time was fitting for him who was to see the Lord and enjoy His conversation, in which both the sojourner of this world would be figuratively represented, and irradiated by the light of true heavenly grace, and zealously enflamed with the love of divine contemplation. — Commentary on Genesis (Hexaemeron) Caesarius of Arles : Now where did this happen? "Near the holm-oak of Mamre," which in Latin is interpreted as "vision" or "discernment." Do you see what kind of a place it is in which the Lord can have a feast? The vision and discernment of Abraham delighted him; he was clean of heart, so that he could see God. Therefore in such a place and in such a heart the Lord can have his feast. Of this vision our Lord spoke to the Jews in the Gospel when he said, "Abraham rejoiced that he was to see my day. He saw it and was glad." He saw my day, he says, because he recognized the mystery of the Trinity. He saw the Father as day, the Son as day, the Holy Spirit as day, and in these three one day. Thus the Father is God, the Son is God, the Holy Spirit is God, and these three are one God. For individually each person is complete God, and all three together are one God. Moreover, because of the unity of substance, in those three measures of flour the Father, Son and Holy Spirit are not unfittingly understood. However, this can also be taken in another way by understanding Sarah as the church; the three measures of flour then are faith, hope and charity. In these three virtues all the fruits of the church are contained, so that if one merits to possess the three within oneself, one can with security receive the entire Trinity at the banquet of one's heart. — SERMON 83.5 Eusebius of Caesarea : Thus the Lord God is said to have appeared as a common man to Abraham while he was seated by the oak of Mamre. But [Abraham] immediately fell down, although he saw a man with his eyes, and worshiped him as God, besought him as Lord and confessed that he was not ignorant as to who he was, using these very words, "O Lord, judge of all the earth, will you not judge righteously?" For if it should be unreasonable to suppose that the unbegotten and immutable substance of God the Almighty was changed into the form of man and, in turn, that the eyes of the beholders were deceived by the phantasm of something created and that such things were falsely invented by Scripture, who else could be proclaimed God and the Lord who judges all the earth and judges righteously, appearing in the shape of a man—if it be not proper to call him the first cause of all things—than his preexistent Word alone? — ECCLESIASTICAL HISTORY 1.2.7-8 Jerome : [Daniel 8:15] "And it came to pass that when I, Daniel, had seen the vision, I sought to understand it." He beheld the vision by way of a picture or likeness, and he failed to understand it. Consequently, not everyone who sees comprehends what he has seen; it is just as if we read the Holy Scripture with our eyes and do not understand it with our heart, "...And behold, one stood before me who resembled the appearance of a man." Angels, after all, are not actually men by nature, but they resemble men in appearance. For example, three persons appeared as men to Abraham at the oak of Mamre (Genesis 18:1-2), and yet they certainly were not men, for one of them was worshipped as the Lord. And so the Savior also stated in the Gospel: "Abraham beheld My day; he beheld it and rejoiced" (John 8:56). — St. Jerome, Commentary on Daniel, CHAPTER EIGHT Origen of Alexandria : But let us now see what is also said in what follows. "But Abraham himself," it says, "was standing by them under the tree." For narratives of this kind we require circumcised ears. For it is not to be believed that it was of the greatest concern to the Holy Spirit to write in the books of the law where Abraham stood. For what does it profit me, who have come to hear what the Holy Spirit teaches the human race, if I should hear that "Abraham was standing under a tree"? But let us see what this tree is, under which Abraham was standing and displaying a banquet to the Lord and to the angels. "Under the tree," it says, "of Mamre." "Mamre" in our language is interpreted as vision or clear-sightedness. Do you see who and what kind is the place in which the Lord can hold a banquet? The vision and clear-sightedness of Abraham delighted him. For he was pure in heart, so that he could see God. In such a place, therefore, and in such a heart, the Lord can hold a banquet with his angels. Finally, in earlier times the prophets were called seers. — HOMILIES ON Genesis 4.3 Augustine of Hippo : APPEARANCE OF THE THREE ANGELS TO ABRAHAM. — And having seen them he ran to meet them from the door of his tent, and did obeisance to the ground. And he said, Lord, if indeed I have found grace in your sight, pass not by your servant . We can ask why, when there were three who appeared to him, he called him Lord in the singular, saying, Lord, if I have found grace in your sight. Is it perhaps because he believed that one of them was the Lord and the other angels? Or rather, perceiving the Lord in the angels, he chose to speak to the Lord rather than to the angels, because when there remained one with Abraham, the other two are sent to Sodom and Lot speaks to them as if he were speaking to the Lord? [ — QUESTIONS ON GENESIS, Q. 32 (tr. J. Litteral, draft)