"In the grove" refers to more than one tree. This alludes to the two principal trees: the Tree of Life, and the Tree of Knowledge of Good and Evil. The spiritual aspect of the Tree of Knowledge of Good and Evil is that the evil forces associated with this tree try to transfer their wicked influence to the good part of anything, in order to exchange evil for good. This is true for all items of creation, and especially true regarding man, who can in this way be driven away from the Tree of Life. Just as Avraham's struggle over evil resulted in Hashem’s appearing to him, so is it with any person living in this world. Only after struggling with the evil found in this world and separating and elevating good from evil, will a person merit a revelation of Hashem.
"As he was sitting at the door of the tent in the heat of the day." The "sitting" in this verse alludes to remaining stationary for a long period of time. Our verse is referring to Avraham's patiently waiting just right outside the gates of holiness for long periods of time, before Hashem revealed Himself to Avraham. The verse in Hallel refers to Avraham's gate as the is says, "This is the gate which belongs to Hashem, the righteous [Avraham, and all those people like him] shall enter through it" (Psalms 118:20). However, when a person wants to enter the gate of holiness he gets tremendous resistance from the forces of evil, who can manifest themselves as confusing thoughts, attacks from family members or other people, all sorts of troubles, etc. The closer one gets to the gate of holiness the more resistance one encounters from the forces of evil, who are guarding the entrance. Many people who reach the gate of holiness turn back because they don’t realize that all the resistance they are encountering is only because they have reached the gates of holiness. They turn back thinking it is too difficult to break through the resistance. Avraham patiently waited, "sitting at the door of the tent," until Hashem had mercy on him and allowed him to pass through the resistance to enter the gate.
"In the heat of the day" refers to the heat of passion inflamed by the evil inclination. We must learn from Avraham's example that even though we are burning with the heat of passion caused by evil inclination, and even if we have succumbed to the evil inclination many times, we must continue to wait patiently for a long time at the gates of holiness while the forces of evil don’t let us in. Even though the heat of his passions was so intense, Avraham did not yield and move from his place, waiting just outside the date of holiness. He just sat there until Hashem had compassion on him and helped him enter the gate. We must certainly do the same.
Yehoshua did the same thing, as the verse says, "but his (Moshe’s) attendant, Yehoshua the son of Nun, a young man (na'ar) didn’t depart from the tent" (Shemos 33:11). The meaning of Yehoshua’s name is, "Hashem will save him." Save him from what? From the bad advice of the evil inclination, which tries to seduce a person at all times. "Yehoshua was a young man (na'ar)". This phrase refers to the possibility that even though a person has made many foolish mistakes and committed many acts of na'arot, youthful foolish behavior, even so, "he didn't depart from the tent [of holiness]", but waited for long periods of time by the tent’s door until he slowly forced is way in the tent and he didn’t depart from patiently waiting to enter. (Lekutai Halachot: Even Haezer: Hilchot Eshis 4:19)
Even though the angels ate with the highest decree of sanctity (as is fitting for angels), nevertheless, the angels did not finish their meal totally untainted and unaffected by their experience of eating food. The angels made mistakes in the performance of carrying out their missions, due to the influence of the physicality contained in the food they had eaten. The Rabbis say as a punishment for their mistakes, two of the angels were not permitted to return to heaven until the time of Yakov. The third angel was not allowed to return to heaven until the time of Shimshon's father, Monoach. Why did these angels make mistakes in carrying out their missions? Due to the physicality of this world, it is difficult for even angels to emerge from this world in a complete state of purity. This is why when an angel returns to heaven after carrying out a mission, he must immerse himself in a river of fire called Dinur to purify himself from the negativity he contracted by being in this world.
The main action in elevating the good which is found in this world from being trapped in the evil of this world is by eating with holiness. Why is the rectification of eating with holiness possible in this world? Since Adam sinned through eating, this caused the evil forces to become intermixed with every physical thing in this world. Therefore, the main emergence of the forces of evil into this world was due to eating, which then allowed the negative forces to enter further into this world.
Therefore, Avraham gave the angels food to give them a full awareness of the gross physicality of this world, to let them experience how it could weigh a person down spiritually, preventing him from approaching holiness. By feeding the angels, Avraham was trying to convince them not to protest the giving of the Torah to the Jews in the future, for it is impossible to stand up to the physicality of this world without the Torah. Learning the Torah is the same as eating with holiness, and helps protect a person from the physicality of this world and can spiritually elevate a person and the world. Rabbi Nachman explains that when food is digested into a person’s body, his soul derives absolutely no nourishment from the physical food itself. The main component that keeps a person alive is his soul, which itself must receive nourishment to remain in the body. What then nourishes the soul? It is the spiritual essence that is contained in one’s food. Eating non-kosher foods, which contain evil forces, is therefore very detrimental to the health of one’s soul. When one learns Torah he directly absorbs spiritual light, which is the necessary nourishment for one’s soul which actually keeps one alive. There are many different areas of study and many different types of mitzvas, because each soul has different nutritional needs. Therefore, learning Torah is like eating with holiness, because it nourishes the soul directly from the Tree of Life. This is why Moshe, when he was in heaven receiving the Torah, was able to survive a total of 120 days without eating and drinking. Moshe was so holy and spiritual that his soul was able to absorb direct nourishment for his soul from the spirituality of the Torah itself, without having to absorb this nourishment through the medium of physical food. We, who are more attached to the physical, can only attain this spiritual nourishment through the medium of eating physical food. The Manna the Jews ate for forty years in the desert is in the same category as what Moshe experienced while in heaven.
When Moshe came to receive the Torah, the angels protested. Hashem, however, reminded the angels that they too had eaten in this world by the tent of Avraham, and they should clearly realize how difficult it is for man to rise above the physicality of this world. Without a Torah, which is the spiritual food which helps a person survive the unholy elements of this world, man is unable to elevate himself. As the verse illustrates, "unless your Torah had been my delight, I would have long since been lost in my affliction [the difficulties of this world]" (Psalms 119:92).
Therefore, when the third angel who had visited Avraham came, after many years of being denied access to return to heaven, to Monoach, Shimshon's father, to inform him of the future birth of Shimshon, the angel refused to eat anything offered to him by Monoach. At this time the angels punishment had come to an end, and he was now permitted to return to heaven. The angel did not want to contaminate himself with food again as he did at Avraham’s tent and possibly delay his return to heaven even longer. (Likutei Halachot: Or Hachayim: Hilchot Bezeas Hapas 5:49.)
Therefore, Avraham fed the angels forbidden food to demonstrate that the Torah is not necessary for angels, since the spiritual laws of negative forces of this world do not apply to them. Hashem said to the protesting angels, you ate from the forbidden mixture of milk and meat, which proves that angels do not need the Torah, since evil forces do not apply to them. However, humans, who are greatly affected by evil, need the Torah and therefore must not eat meat and milk together. Thus, it was due to the mitzvah of not eating meat and milk together that silenced the angels’ protests against giving the Jews the Torah. (Lekutai Halachot, Yoreh Dayeh: Hilchot Dom 1:5)
The Rabbis tell us that in the merit of Avraham saying, "I am dust and ashes," his descendants merited the two mitzvot of the dust: the mitzvah of Sota (a woman suspected of adultery) and the mitzvah of the Para Aduma (which is part of the purification process for the coming in contact with the dead). What connection does dust have to these two mitzvot? As a result of Adam’s sin falsehood, death, and evil came to the world. To nullify the possible false denial of a woman suspected of adultery, she is given to drink a liquid containing dirt which injects her with the power of truth to help her overcome a possible false denial.
When a person comes in contact with the dead, he encounters the forces of evil, which brought death to this world as a result of Adam's sin. These forces of evil are filled with falsehood. Therefore, to be cleansed of these forces of evil which contain falsehood, one must be sprinkled with the dust of the red heifer to be injected with truth which drives away the forces of evil. This is why the snake, who is the spiritual source of all evil and falsehood in this world, was cursed as follows, "upon your belly shall you go [to crawl in the dirt, which contains the truth] and dust shall you eat all the days of your life" (Bereshis 3:14). Hashem cursed the snake in this manner to inject the spiritual power of truth into the spiritual source of all evil and falsehood in order to nullify its power of falsehood in the world. The snake’s evil would now be neutralized by being constantly connected to the truth, contained in the dirt. The dirt contains truth as the verse says, "Truth will sprout from the earth."
This is why the Jewish People are compared to the dirt, as the verse says, "And I [Hashem] will make your [Avraham’s] seed as the dust of the earth" (Bereshis 13:16.). The Jewish People must be connected to the dust of this world, which has the spiritual power of truth, for the Jewish People are spiritually the main good and truth of this world.
"May the sprout of Your servant David quickly sprout" (from weekday Shmonei Esrai.), from the dust, which will bring the truth of Hashem to this world Amen. (Lekutai Halachot: Yorah Dayah- Hilchot Bihamah V’chaya Tehorah 4:26-29.)