Midrash Tanchuma, Vayera 3

‎בְּאֵלֹנֵי מַמְרֵא. וְלָמָּה בְּאֵלֹנֵי מַמְרֵא? יִתְבָּרַךְ שְׁמוֹ שֶׁל הַקָּדוֹשׁ בָּרוּךְ הוּא שֶׁאֵינוֹ מְקַפֵּחַ שָׂכָר שֶׁל כָּל בְּרִיָּה. שְׁלֹשָׁה אוֹהֲבִים הָיוּ לְאַבְרָהָם: עָנֵר אֶשְׁכּוֹל וּמַמְרֵא. וְכֵיוָן שֶׁאָמַר לוֹ הַקָּדוֹשׁ בָּרוּךְ הוּא שֶׁיִּמּוֹל, הָלַךְ לָקַחַת מֵהֶם עֵצָה. הָלַךְ אֵצֶל עָנֵר, אָמַר: כָּךְ וְכָךְ אָמַר לִי הַקָּדוֹשׁ בָּרוּךְ הוּא. אָמַר לוֹ: עָנֵר: בַּעַל מוּם רוֹצֶה אַתָּה לַעֲשׂוֹתְךָ שֶׁיִּהְיוּ קְרוֹבֵיהֶן שֶׁל הַמְּלָכִים שֶׁהָרַגְתָּ בָּאִין וְהוֹרְגִין אוֹתְךָ וְאֵין אַתָּה יָכוֹל לִבְרֹחַ מִפְּנֵיהֶם? הִנִּיחוֹ וְהָלַךְ אֵצֶל אֶשְׁכֹּל, אָמַר לוֹ: כָּךְ וְכָךְ אָמַר לִי הַקָּדוֹשׁ בָּרוּךְ הוּא. אָמַר לוֹ אֶשְׁכּוֹל: אַתָּה זָקֵן, אִם אַתָּה תָמוּל יֵצֵא מִמְּךָ דָּם הַרְבֵּה וְלֹא תוּכַל לִסְבֹּל וְתָמוּת. הִנִּיחוֹ וְהָלַךְ אֵצֶל מַמְרֵא, אָמַר לוֹ: כָּךְ וְכָךְ אָמַר לִי הַקָּדוֹשׁ בָּרוּךְ הוּא: מַה תְּיַעֲצֵנִי? אָמַר לוֹ מַמְרֵא: בַּדָּבָר הַזֶּה אַתָּה מְבַקֵּשׁ עֵצָה, הֲלֹא הוּא שֶׁהִצִּילְךָ מִכִּבְשַׁן הָאֵשׁ וְעָשָׂה לְךָ כָּל הַנִּסִּים, וְהִצִּילְךָ מִן הַמְּלָכִים, וְאִלּוּלֵי כֹחוֹ וּגְבוּרָתוֹ הָיוּ הוֹרְגִין אוֹתְךָ, וְהִצִּיל רַמַ״‎ח אֵבָרִים שֶׁבָּךְ, וּמִקְצָת אֵבֶר אֶחָד אַתָּה מְבַקֵּשׁ עֵצָה, עֲשֵׂה כְּמִצְוָתוֹ. אָמַר הַקָּדוֹשׁ בָּרוּךְ הוּא יִתְבָּרַךְ, אַתָּה שֶׁנָּתַתָּ עֵצָה שֶׁיִּמּוֹל, אֵינִי נִגְלֶה אֵלָיו אֶלָּא בִּתְחוּמָךְ, הֲדָא הוּא דִכְתִיִב: וַיֵּרָא אֵלָיו ה' בְּאֵלֹנֵי מַמְרֵא.

And the Lord appeared unto him by the terebinths of Mamre (Gen. 18:1) Why did the Holy One, blessed be He, appear by the terebinths of Mamre? May the name of the Holy One, blessed be He, be blessed, for He does not withhold a reward from any of His creatures. Abraham had three friends, Aner, Eshkol, and Mamre, and when the Holy One commanded Abraham to circumcise himself, he consulted each of them. He went first to Aner and related to him what the Holy One had said. Aner replied: “Do you wish to cripple yourself so severely that when the descendants of the kings whom you have slain attack, you will be unable even to flee from them?” He left him and went to Eshkol and told him what the Lord had commanded. Eshkol responded: “You are an old man, and if you are circumcised, considerable blood will flow from you, and you will not be able to survive the loss and will perish.” Whereupon he departed from him, and went to Mamre and said: “What do you advise?” Mamre retorted: “Need you seek my advice in such a matter? Did He not release you from the fiery furnace, perform miracles in your behalf, and rescue you from kings? The fact is that you would have been destroyed long ago were it not for His strength and His might. He saved your two hundred and forty-eight limbs, and yet you ask advice concerning merely a piece of one of your organs. Do as He has commanded!” Thereupon the Holy One, blessed be He, exclaimed: Blessed shall you be for having advised him to be circumcised; I shall reveal Myself to him only in your territory. Hence, it is written: The Lord appeared unto him by the terebinths of Mamre.

וְהוּא ישֵׁב פֶּתַח הָאֹהֶל כְּחֹם הַיּוֹם, מַהוּ כְּחֹם הַיּוֹם? הִרְתִּיחַ הַקָּדוֹשׁ בָּרוּךְ הוּא אוֹתוֹ הַיּוֹם, כְּדֵי שֶׁלֹּא יְהוּ עוֹבְרִים וְשָׁבִים בָּאִים וְיֵלֵךְ אַבְרָהָם וְיִצְטַעֵר לְהַכְנִיסָם לְכַלְכְּלָם.

And he sat in the tent door in the heat of the day (Gen. 18:1). Why the heat of the day? It indicates that the Holy One, blessed be He, had made the day extremely hot so that no travelers would pass by, necessitating Abraham to fuss over them.

דָּבָר אַחֵר, עַד שֶׁיָּפוּחַ הַיּוֹם, זֶה יוֹם הַדִּין, שֶׁנֶּאֱמַר: כִּי הִנֵּה הַיּוֹם בָּא בֹּעֵר כַּתַּנּוּר וְהָיוּ כָל זֵדִים וְכָל עֹשֶׂה רִשְׁעָה קַשׁ וְלִהֵט אֹתָם הַיּוֹם הַבָּא אָמַר ה' צְבָאוֹת אֲשֶׁר לֹא יַעֲזֹב לָהֶם שֹׁרֶשׁ וְעָנָף (מלאכי ג, יט).

Another explanation. Until the day breatheth (Song 4:6). This refers to judgment day, as it is said: For, behold, the day cometh, it burneth as a furnace; and all the proud, and all that work wickedness, shall be stubble; and the day that cometh shall set them ablaze, saith the Lord of hosts, that it shall leave them neither root nor branch (Mal. 3:19).

וְנָסוּ הַצְּלָלִים, שֶׁאֵין בּוֹ צֵל לָרְשָׁעִים, שֶׁנֶּאֱמַר: אֵין חֹשֶׁךְ וְאֵין צַלְמָוֶת לְהִסָּתֶר שָׁם פֹּעֲלֵי אָוֶן (איוב לד, כב).

And the shadows flee away (Song 4:6). This indicates that on that day there will be no shadow for the wicked, as it is said: There is no darkness and shadow of death, where the workers of iniquity may hide themselves (Job 24:32).

אֵלֶךְ לִי אֶל הַר הַמּוֹר, זֶה בֵּית הַמִּקְדָּשׁ שֶׁהָיוּ מַקְרִיבִין בּוֹ מוֹר. וְאֶל גִּבְעַת הַלְּבוֹנָה, זוֹ יְרוּשָׁלַיִם שֶׁהָיוּ מַקְרִיבִין בְּמִנְחוֹתֵיהֶם לְבוֹנָה.

I will get me to the mountains of myrrh (Song 4:6) refers to the Temple, in which they brought offerings of myrrh. And to the hill of frankincense (ibid.) alludes to Jerusalem, whither they brought their offerings of frankincense.