Another interpretation of "garments of skin": Rabbi Elazar said, from the skin that the serpent shed, the Holy One, blessed be He, took and made garments of honor for Adam and for his helper. At twilight at the going-out of the Sabbath, Adam was thinking in his heart: Woe is me, perhaps the serpent that led me astray will come and bite me. And a pillar of fire was sent to him to give him light and to guard him from all evil. Adam saw it and rejoiced in his heart, and he stretched out his hands toward its light and said, "Blessed are You, O LORD, Creator of the lights of the fire." He said: Now I know that the holy day is distinguished from the weekday, for one must not kindle fire on the Sabbath day. And whoever recites the Havdalah at the going-out of the Sabbath, or hears it from the one who recites it, the Holy One, blessed be He, calls him holy and a treasured possession, and saves him from the trouble of the nations, as it is said, "And you shall be My treasured possession from among all the peoples" (Exodus 19:5). On the first day of the week Adam entered the waters of the upper Gichon until the water reached his neck, and he fasted seven weeks of days until his body became like a sieve. [Adam said:] While I am still alive let me build for myself a resting place for my repose. He said: If the tablets, because they are destined to be written by the finger of the Holy One, blessed be He, cause the waters of the Jordan to flee before them, then my body, which His two hands shaped and the breath of the spirit of His mouth that He breathed into my nostrils - how much more so. And after my death they will come and take my bones and make them into idolatry. Rather, I will sink my coffin deep down in the earth, a cave within a cave, and therefore it is called the Cave of Machpelah [the doubled cave].
Adam Blesses the First Fire and Hides His Bones in the Cave
Yalkut Shimoni on Torah 34:2
דָּבָר אַחֵר, כָּתְנוֹת עוֹר, אָמַר רַבִּי אֶלְעָזָר, מִן הָעוֹר שֶׁהִפְשִׁיט הַנָּחָשׁ לָקַח הַקָּדוֹשׁ בָּרוּךְ הוּא וְעָשָׂה לָהֶם כָּתְנוֹת כָּבוֹד לְאָדָם וּלְעֶזְרוֹ. בֵּין הַשְּׁמָשׁוֹת דְּמוֹצָאֵי שַׁבָּת הָיָה אָדָם מְהַרְהֵר בְּלִבּוֹ אוֹי לִי שֶׁמָּא הַנָּחָשׁ שֶׁהִתְעָה אוֹתִי יָבוֹא וִישׁוּפֵנִי, וְנִשְׁתַּלַּח לוֹ עַמּוּד שֶׁל אֵשׁ לְהָאִיר לוֹ וּלְשָׁמְרוֹ מִכָּל רָע. רָאָה אָדָם וְשָׂמַח בְּלִבּוֹ וּפָשַׁט יָדָיו לְאוֹרוֹ וְאָמַר בָּרוּךְ אַתָּה ה' בּוֹרֵא מְאוֹרֵי הָאֵשׁ. אָמַר, עַכְשָׁו אֲנִי יוֹדֵעַ שֶׁנִּבְדָּל יוֹם הַקֹּדֶשׁ מִיּוֹם הַחוֹל שֶׁאֵין לְהַבְעִיר אֵשׁ בְּיוֹם הַשַּׁבָּת וְכָל מִי שֶׁמַּבְדִּיל בְּמוֹצָאֵי שַׁבָּת אוֹ שׁוֹמֵעַ מִן הַמַּבְדִּיל הַקָּדוֹשׁ בָּרוּךְ הוּא קוֹרֵא לוֹ קָדוֹשׁ וּסְגֻלָּה, וּמַצִּילוֹ מִצָּרַת הָעַמִּים, שֶׁנֶּאֱמַר "וִהְיִיתֶם לִי סְגֻלָּה מִכָּל הָעַמִּים". בְּאֶחָד בְּשַׁבָּת נִכְנַס אָדָם בְּמֵימֵי גִּיחוֹן הָעֶלְיוֹן עַד שֶׁהִגִּיעוּ הַמַּיִם עַד צַוָּארוֹ וְהָיָה מִתְעַנֶּה שֶׁבַע שַׁבְּתוֹת יָמִים עַד שֶׁנַּעֲשָׂה גּוּפוֹ כְּלִבּוֹ עַד שֶׁאֲנִי בַּחַיִּים אֶבְנֶה לִי בֵּית מָלוֹן לְרִבְצִי אָמַר, וּמַה הַלּוּחוֹת עַל יְדֵי שֶׁהֵן עֲתִידִין לִכְתּוֹב בְּאֶצְבָּעוֹ שֶׁל הַקָּדוֹשׁ בָּרוּךְ הוּא עֲתִידִין מֵימֵי הַיַּרְדֵּן לִבְרֹחַ מִפְּנֵיהֶם גּוּפִי שֶׁגָּבְלוּ שְׁתֵּי יָדָיו וְרוּחַ נִשְׁמַת פִּיו שֶׁנָּפַח בְּאַפִּי עַל אַחַת כַּמָּה וְכַמָּה וּלְאַחַר מִיתָתִי יָבוֹאוּ וְיִקְחוּ אֶת עַצְמוֹתַי וְיַעֲשׂוּ לָהֶם ע"ז, אֶלָּא הֲרֵינִי מַעֲמִיק אֶת אֲרוֹנִי לְמַטָּה בָּאָרֶץ, מְעָרָה לִפְנִים מִמְּעָרָה, לְפִיכָךְ נִקְרֵאת מְעָרַת הַמַּכְפֵּלָה.