Or HaChaim on Genesis 18:2/אור החיים על בראשית י״ח:ב׳

1 וישא עיניו וידא. When he raised his eyes he saw, etc. Why did the Torah add the word והנה?" Besides, why did the Torah add that the three men נצבים, "were standing?" This is no more than normal! What does the addition of that word add to our understanding? Furthermore, what is the meaning of the word עליו, "upon him?" The meaning of that word cannot be that they were merely close to Abraham! If that were the case, why did Abraham have to run towards them? Another difficulty in the paragraph is the repetition of the word וירא! Why does the Torah portray Abraham as bowing down to these men before he knew who they were, i.e. angels and not Arabs?

2We must understand the report of the Torah in terms of what transpired later, i.e. that the men were indeed angels who appeared in human garb in order to partake of Abraham's hospitality for reasons known to us. The words וירא והנה simply mean that Abraham saw that they were apparently men, something which later on proved to have been an error on his part. He had judged the outward appearance. Had the Torah not added the word והנה, the report would have been a lie.

3The word נצבים means that Abraham, who was by now familiar with celestial messengers, realised that these "men" had been sent to him for a specific purpose, for his sake. One of them, for instance, had been charged with the task of healing him. A second one had been sent to inform him that by that time in the following year Sarah would have a son. The third one, whose task appeared to be the destruction of Sodom, nevertheless had detoured in order to afford Abraham an oppportunity to intercede on behalf of the people of Sodom before G'd would carry out His judgment on that city. In other words, his whole presence there was "עליו, on account of him (Abraham)."

4The expression אנשים נצבים may allude to the human posture these angels assumed. The word עליו means "on his account," i.e. for his sake, so that he could perform the מצוה of hospitality. Abraham realised that they were angels because the bearing of an angel cannot be disguised. We know this already from the wife of Manoach (Judges 13,2). If that lady realised that she faced an angel, someone of Abraham's stature would certainly be aware of the presence of an angel. After all, Abraham had already encountered angels previously. The word וירא a second time merely confirmed Abraham's original impression seeing that he had been healed and was able to run towards them. An angel has long-distance vision and inasmuch as the cure he performs is of a spiritual nature, he does not need to be physically close to the patient. As soon as Abraham felt cured, he bowed down to the angel in gratitude to G'd.