And he lifted up his eyes and looked, and, lo, three men stood by him: and when he saw them, he ran to meet them from the tent door, and bowed himself toward the ground,
Read Chapter 18
Ambrose of Milan
Hospitality is a good thing, and it has its recompense: first of all the recompense of human gratitude and then, more importantly, the divine reward. In this earthly abode we are all guests; here we have only a temporary dwelling place. We depart from it in haste. Let us be careful not to be discourteous or neglectful in receiving guests, lest we be denied entrance into the dwelling place of the saints at the end of our life. For this reason, the Savior said in the Gospel, “Make friends for yourselves by means of unrighteous mammon, so that when it fails they may receive you into the eternal habitations.” Moreover, while we are in this body, there often arises the necessity of traveling. Therefore that which you will have denied to others, you will have decided against yourself. You must show yourself worthy of that which you will have offered to others. If all decided not to receive guests, where would those who are traveling find rest? Then we would have to abandon human habitations ...
“Three men came to Abraham and stood over him.” Observe how it is that they come upon him but not against him. He had subjected himself to God’s will, and for this reason God is said to stand over him. “They stood over him,” not against him to repulse him but over him for protection.
Notice, brothers, and see how God appeared to Abraham and how he appeared to Lot. The three men came to Abraham and stood over him; two came to Lot and stayed in the street. Consider, brothers, whether these things did not happen through the dispensation of the Holy Spirit according to their merits. Indeed, Lot was far inferior to Abraham; if he had not been, he would not have merited to be separated from Abraham, nor would the dwelling of Sodom have pleased him. Now the three men came to Abraham at noon, while the other two came to Lot in the evening for this reason: Lot was unable to endure the power of the noonday sun, but Abraham could stand its full brightness.
Although Abraham ran from the tent toward them as if toward strangers, he ran to receive those strangers with love. His love for strangers was thus proved by the haste with which he ran to meet those strangers. Therefore the Lord, who had just appeared to him at the door of the tent, now appeared to Abraham clearly in one of the three. Abraham then fell down and worshiped him, seeking from him in whom majesty dwells that he condescend to enter his house and bless his dwelling. “If I have found favor in your sight, do not pass by your servant.” God did not oppose him, for he said, “Do as you have said.” Then Abraham ran to Sarah [telling her] to make three measures of wheat, and then he ran to the herd to get a fatted calf.
Men in outward appearance, but angels indeed. (Hebrews xiii. 2; St. Augustine, City of God xvi. chap. 29.) Some have supposed, that one of them was the Son of God, whom Abraham adored, and who bears throughout the chief authority. Tres vidit et unum adoravit. He saw three and adored one, as we read in the Church office. In the former supposition, which is generally adopted, this adoration was only a civil ceremony, if Abraham considered them as mere men; or it might be mixed with a degree of religious, though inferior veneration, if he imagined they were angels; or in fine, he adored God in his representatives. (Haydock)