As Avraham enters into the covenant, he circumcises himself in his old age. The first we learn of him afterwards, the first act by the first religious person, is that as he recuperated in the blazing heat, he looked for guests:
וַיֵּרָא אֵלָיו ה בְּאֵלֹנֵי מַמְרֵא וְהוּא ישֵׁב פֶּתַח הָאֹהֶל כְּחֹם הַיּוֹם. וַיִּשָּׂא עֵינָיו וַיַּרְא וְהִנֵּה שְׁלשָׁה אֲנָשִׁים נִצָּבִים עָלָיו וַיַּרְא וַיָּרָץ לִקְרָאתָם – God appeared to him in Mamre, while he was sitting at the door in the heat of the day. He looked up and saw three men approaching, and he ran towards them. (18:1-2)
They were no ordinary guests. It turns out that they were angels, on a mission, who anticipated the birth of Yitzchak. Avraham then has an encounter with God, in which God tells him a secret:
וַהֹ אָמָר הַמֲכַסֶּה אֲנִי מֵאַבְרָהָם אֲשֶׁר אֲנִי עֹשֶׂה. אַבְרָהָם הָיוֹ יִהְיֶה לְגוֹי גָּדוֹל וְעָצוּם וְנִבְרְכוּ בוֹ כֹּל גּוֹיֵי הָאָרֶץ. כִּי יְדַעְתִּיו לְמַעַן אֲשֶׁר יְצַוֶּה אֶת בָּנָיו וְאֶת בֵּיתוֹ אַחֲרָיו וְשָׁמְרוּ דֶּרֶךְ יְהֹוָה לַעֲשׂוֹת צְדָקָה וּמִשְׁפָּט לְמַעַן הָבִיא יְהֹוָה עַל אַבְרָהָם אֵת אֲשֶׁר דִּבֶּר עָלָיו – God said, “Shall I hide what I am doing from Avraham? Avraham will be great, and through him, the world will be blessed. I know he instructs his children, and their children after them, to preserve the way of God; to do what is right and practice justice…” (18:17-19)
Yet Avraham is the last person who needs to be instructed to avoid the ways of Sdom! The setting of the conversation is that in his weakest moment, he actively looks for tired travellers to feed, bathe, and take care of – the anathema of Sdom. So why warn him if he was above it?
Rav Hirsch explains that parsing Hashem’s thoughts carefully, Hashem wasn’t concerned for Avraham at all.
Hashem shared His plan with Avraham because he was someone who would teach his family to do the right thing. The conversation stands forever, for בֵּיתוֹ אַחֲרָיו, to draw a stark contrast.
An old, sick, haggard, and weary Avraham, at his lowest and worst, is the benchmark of humanity, compared to Sdom, a vibrant, wealthy and successful commercial hub.
Rav Hirsch emphasises how this contrast is the very first lesson we learn after Avraham circumcises himself, entering the covenant that could set him apart, did not. He was in Mamre, land belonging to his old friends and allies. Yet he was out looking for pagan idolators to entertain; there was no-one else he could expect! He gave his mysterious guests incredible luxury, freshly prepared.
That is the first encounter the world has with people of the covenant.
Avraham himself was overjoyed that people would not think he was strange or different. His relationship with greater mankind was only enhanced.
Our role model was not someone who hid away from the world to focus on spirituality and mystical holiness. He went out into the world, engaged with it, and made it better through his interactions. The descendants of Avraham are charged with being the most humane of men – to show a better way to be; with open hearts, and open hands.