Genesis 18:2

2. And, lo, three men stood by him. Before Moses proceeds to his principal subject, he describes to us, the hospitality of the holy man; and he calls the angels men, because, being clothed with human bodies, they appeared to be nothing else than men. And this was done designedly, in order that he, receiving them as men, might give proof of his charity. For angels do not need those services of ours, which are the true evidences of charity. Moreover, hospitality holds the chief place among these services; because it is no common virtue to assist strangers, from whom there is no hope of reward. For men in general are wont, when they do favors to others, to look for a return; but he who is kind to unknown guests and persons, proves himself to be disinterestedly liberal. Wherefor the humanity of Abraham deserves no slight praise; because he freely invites men who were to him unknown, through whom he had no advantage, and from whom he had no hope of mutual favors. What, therefore, was Abraham’s object? Truly, that he might relieve the necessity of his guests. He sees them wearied with their journey, and has no doubt that they are overcome by heat; he considers that the time of day was becoming dangerous to travelers; and therefore he wishes both to comfort, and to relieve persons thus oppressed. And certainly, the sense of nature itself dictates, that the strangers are to be especially assisted; unless blind self love rather impels us to mercenary services. For none are more deserving of compassion and help than those whom we see deprived of friends, and of domestic comforts. And therefore the right of hospitality has been held most sacred among all people, and no disgrace was ever more detestable than to be called inhospitable. For it is a brutal cruelty, proudly to despise those who, being destitute of ordinary, have recourse to our assistance. It is however asked, whether Abraham was wont, thus to receive indiscriminately all kinds of guests? I answer that, according to his accustomed prudence, he made his distinction between his guests. And truly, the invitation, which Moses here relates, has something uncommon. Undoubtedly, the angels bore, in their countenance and manner, marks of extraordinary dignity; so that Abraham would conclude them to be worthy not only of meat and drink, but also of honor. They who think that he was thus attentive to his office, because he had been taught, by his fathers, that the angels often appeared in the world in human form, reasons too philosophically. Even the authority of to Apostle is contrary to this; for he denies that they were, at first, known to be angels either by Abraham, or by Lot, since they thought they were entertaining men. (Hebrews 13:2) This, then is to be maintained; that when he saw men of reverend aspect, and having marks of singular excellence, advancing on their journey, he saluted them with honor, and invited them to repose. But at that time, there was greater honesty than is at present, to be found amid the prevailing perfidy of mankind; so that the right of hospitality might be exercised with less danger. Therefore, the great number of inns are evidence of our depravity, and prove it to have arisen from our own fault, that the principal duty of humanity has become obsolete among us.

And bowed himself toward the ground. This token of reverence was in common use with oriental nations. The mystery which some of the ancient writers have endeavored to elicit from this act; namely, that Abraham adored one out of the three, whom he saw, and, therefore perceived by faith, that there are three persons in one God, since it is frivolous, and obnoxious to ridicule and calumny, I am more than content to omit. For we have before said, that the angels were so received by the holy man, as by one who intended to discharge a duty towards men. But the fact that God honored his benignity, and granted it to him as a reward, that angels should be presented to him for guests, was that he was not aware of, till they had made themselves known at the conclusion of the meal. It was therefore a merely human and civil honor, which he paid them. As to his having saluted one in particular, it was probably done because he excelled the other two. For we know that angels often appeared with Christ their Head; here, therefore, among the three angels, Moses points out one, as the Chief of the embassy.