The parasha opens with Avraham sitting in wait at the entrance to his tent and, despite recovering from surgery, he is hoping for a passerby upon whom he can bestow kindness. Three angels – Gavriel, Rafael and Michael – pay him a visit in the form of three Arabian travelers. Avraham runs to greet them and immediately tends to their needs and offers them a feast. This is Avraham, the pillar and paradigm of Chesed, at his best. Despite his personal discomfort, he extends beyond his own world and focuses on the world of another – their needs and their comfort are at the forefront of his mind.
As a reward for this specific act of kindness, Avraham’s descendants, Bnei Yisrael, will enjoy miracles during their sojourn in the desert – as the Midrash describes:
וּמַה פָּרַע הַקָּדוֹשׁ בָּרוּךְ הוּא לְבָנָיו, הַמָּן יוֹרֵד לָהֶם, וְהַבְּאֵר עוֹלָה לָהֶן, וְהַשְּׂלָו מָצוּי לָהֶם, וְעַנְנֵי כָבוֹד מַקִּיפִין אוֹתָם, וְעַמּוּד הֶעָנָן נוֹסֵעַ לִפְנֵיהֶם.
And (for feeding the angels) how did the Holy One blessed be He repay his (Avraham’s) children? He brought down the Mann for them, He brought up the water from the Beer for them, the quale was available to them, and the clouds of glory surrounded them, and the pillar of cloud travelled in front of them… 
What is truly amazing, is that the very same midrash points out that the kindness that Avraham bestowed by feeding the angels was entirely unnecessary from the receiver’s standpoint. As Rashi comments, “they appeared to eat”  but didn’t actually eat – they are angels after all. If so, then all the effort Avraham went to in providing them a feast did not serve any benefit to them whatsoever. In the words of the Midrash:
מִי הוּא שֶׁעָשָׂה חֶסֶד עִם מִי שֶׁלֹּא הָיוּ צְרִיכִין, אַבְרָהָם עִם מַלְאֲכֵי הַשָּׁרֵת, כְּתִיב: וְהוּא עֹמֵד עֲלֵיהֶם תַּחַת הָעֵץ וַיֹּאכֵלוּ, וְכִי אוֹכְלִין הָיוּ, אָמַר רַבִּי יוּדָן נִרְאִין כְּאוֹכְלִין וְשׁוֹתִין
Who is the one who did chesed with one who doesn’t need anything? Avraham with ministering angels. It is written “and he stood over them under the tree and they ate” Were they eating? Rav Yuden said: they appeared as if to be eating and drinking.
Note that the Midrash still refers to this as Chesed even though the receiver didn’t get anything from the giver.
Rav Dessler in Michtav MeEliyahu  writes how this is indeed a chidush – a novelty – in the understanding of chesed. We would normally suppose that the true test of chesed is in how the receiver benefited from the kindness. The greater the beneficence – the greater the act of kindness. Indeed, the Torah’s language on the mitzvah of tzedakah is to give the person דֵּ֚י מַחְסֹר֔וֹ אֲשֶׁ֥ר יֶחְסַ֖ר לֽוֹ – what is sufficient to meet his (the recipient’s) needs . As such, if I give a dollar to a billionaire and he doesn’t even use it, have I really bestowed kindness? One would think not. It is therefore hard to understand why Avraham’s kindness to the angels merited such great miracles from Hashem, since Avraham’s giving here did not in fact fulfill any need at all! But this is the great merit of kindness – that even when the recipient doesn’t need, the giver is rewarded for the effort extended, and it is still called Chesed.
Perhaps the reason for this can be understood when we can extend this lesson to all mitzvot, and say that the mitzvot in general are not only about the positive result they bring to the beneficiary or the world but are also there to refine the person himself, as the Rambam writes:
And all these matters [the mitzvot] are to [help us to] overcome our negative inclinations and to correct our traits; and most laws of the Torah are instruction from afar from the Great Adviser [to help us] to correct our character traits and straighten our ways .
This idea can also be seen in the reverse. An unkind act is still negative to the one who does it, even if the intended insult did not reach the target. This is how the Chofetz Chaim writes regarding lashon hara that isn’t believed by the listener:
And know that even if no harm came to that man (the subject) from his (The speaker’s) lashon hara, as when the listeners did not accept his words, or the like, even so it does not remove it from the category of lashon hara and he requires atonement .
In other words, if the listener refused to believe what he heard and doesn’t pass the story onto anyone, effectively knocking the would-be gossip out of the air – iron dome style – without it causing any damage to the subject, the speaker is still considered to have spoken Lashon Hara and needs to do teshuva. Why? It seems the speaker is still tarnished by the act of denigrating another, even if it didn’t affect the subject at all.
We see then the wonderful wisdom and impact of the Torah and mitzvot, that while simultaneously enlightening the world with their positive effect on others, and connecting one to Hashem, the mitzvot also serve to refine the person who performs them, and this in and of itself, even without the external impact of the mitzvah, is worthy of enormous merit.
This important idea, we learn and receive from our forefather Avraham, as he runs to do kindness at the opening of our parasha,
Have a lovely Shabbos.
 Vayikra Rabah – Behar – 34:8
 Rashi quoting the gemara in Bava Metzia 86b. Here is the gemara: Rabbi Tanḥum bar Ḥanilai says: A person should never deviate from the local custom, as Moses ascended to heaven on high and did not eat bread while he was there, whereas the ministering angels descended down to this world, as guests visiting Abraham, and they ate bread. You say: And they ate bread? Can it enter your mind that they actually ate food? Rather, say that they merely appeared as though they ate and drank.
 Devarim 15:8
 Hilchot Temura 4:13