Midrash Tanchuma, Lech Lecha 11

‎אַחַר הַדְּבָרִים הָאֵלֶּה הָיָה דְבַר ה'. זֶהוּ שֶׁאָמַר הַכָּתוּב, יִצְפֹּן לַיְשָׁרִים תּוּשִׁיָּה מָגֵן לְהֹלְכֵי תֹם (משלי ב, ז). מַהוּ יִצְפֹּן לַיְשָׁרִים תּוּשִׁיָּה? עַד שֶׁלֹּא נִבְרָא הָעוֹלָם צָפַן הַקָּדוֹשׁ בָּרוּךְ הוּא הַתּוֹרָה, עַד שֶׁבָּא אַבְרָהָם וְקִיְּמָהּ, שֶׁנֶּאֱמַר: עֵקֶב אֲשֶׁר שָׁמַע אַבְרָהָם בְּקֹלִי וַיִּשְׁמֹר מִשְׁמַרְתִּי מִצְוֹתַי חֻקּוֹתַי וְתוֹרֹתָי (בראשית כו, ה). After these things the word of the Lord came unto Abram (Gen. 15:1). Scripture says elsewhere in reference to this verse: He layeth up sound wisdom for the righteous; He is a shield to them that walk in integrity (Prov. 2:7). What is the meaning of He layeth up sound wisdom for the righteous? It means that the Holy One, blessed be He, stored the Torah away, prior to the creation of the world, until Abraham came to fulfill it, as it is said: Because that Abraham hearkened to My voice, and kept My charge, My commandments, My statutes, and My Laws (Gen. 26:5).

אָמַר רַבִּי לֵוִי בְּשֵׁם רַבִּי שְׁמוּאֵל בַּר נַחְמָן, תְּשַׁע מֵאוֹת וּשְׁמוֹנִים דּוֹר קִפֵּל הַקָּדוֹשׁ בָּרוּךְ הוּא בִּשְׁבִיל לִתֵּן הַמִּילָה לְאַבְרָהָם, שֶׁנֶּאֱמַר: זָכַר לְעוֹלָם בְּרִיתוֹ דָּבָר צִוָּה לְאֶלֶף דּוֹר (תהלים קה, ח). וַהֲרֵי לֹא נִתְּנָה אֶלָּא לְעֶשְׂרִים דּוֹר, מֵאָדָם עַד נֹחַ עֲשָׂרָה, מִנֹּחַ עַד אַבְרָהָם עֲשָׂרָה, הֲרֵי עֶשְׂרִים וְנִתְּנָה לְאַבְרָהָם. וְרַבִּי יוֹחָנָן בְּשֵׁם רַבִּי יוֹסִי הַגְּלִילִי אוֹמֵר, תְּשַׁע מֵאוֹת שִׁבְעִים וְאַרְבָּעָה דּוֹר קִפֵּל הַקָּדוֹשׁ בָּרוּךְ הוּא בִּשְׁבִיל לִתֵּן תּוֹרָה לְדוֹר הַמִּדְבָּר עַל שֶׁהָיוּ יְשָׁרִים, שֶׁנֶּאֱמַר: יִצְפֹּן לַיְשָׁרִים תּוּשִׁיָּה, R. Levi stated in the name of R. Samuel the son of Nahmani: The Holy One, blessed be He, passed over nine hundred and eighty generations in order to give the law of circumcision to Abraham,¹⁷The divine plan originally contemplated that a thousand generations would pass before the rite of circumcision was introduced. even though it is stated: He hath remembered His covenant, the word which He commanded to a thousand generations (Ps. 105:8). In fact, He gave it to him only after twenty generations had passed by: the ten generations between Adam and Noah and the ten generations between Noah and Abraham—totaling twenty generations in all. Then He gave the law of circumcision to Abraham. R. Yohanan declared in the name of R. Yosé the Galilean: The Holy One, blessed be He, passed over nine hundred and seventy generations in giving the Torah to the generation of the wilderness.¹⁸Actually it was 974 generations that were passed by. Adam to Noah was ten generations, Noah to Abraham was another ten, and Abraham to Moses was six, totaling twenty-six. He did so because it was a righteous generation, as it is said: He layeth up sound wisdom for the righteous (Prov. 2:7).

רַבִּי שְׁמוּאֵל בַּר נַחֲמָנִי אָמַר אַף עֵרוּבֵי תַּבְשִׁילִין שָׁמַר אַבְרָהָם שֶׁנֶּאֱמַר: עֵקֶב אֲשֶׁר שָׁמַע אַבְרָהָם בְּקֹלִי. אָמַר לוֹ הַקָּדוֹשׁ בָּרוּךְ הוּא: אַתָּה עָסַקְתָּ בְּתוֹרָתִי, חַיֶּיךָ שֶׁאֲנִי מָגֵן לָךְ. כְּשֵׁם שֶׁהַמָּגֵן אוֹחֵז הַחֶרֶב אֲפִלּוּ זוֹרְקִים בּוֹ חִצִּים וַאֲבָנִים הַמָּגֵן מְקַבְּלָם, כָּךְ אֲנִי מָגֵן לָךְ. וְלֹא לְךָ בִּלְבַד, אֶלָּא אַף לְבָנֶיךָ אִם יִהְיוּ עוֹסְקִין בְּתוֹרָתִי כְּשֵׁם שֶׁעָסַקְתָּ אַתָּה, כָּךְ אֲנִי נַעֲשֶׂה לָהֶם כְּמָגֵן, שֶׁנֶּאֱמַר: אִמְרַת ה' צְרוּפָה מָגֵן הוּא לְכֹל הַחוֹסִים בּוֹ (ש״‎ב כב, לא). לְכָךְ נֶאֱמַר: מָגֵן לְהֹלְכֵי תֹם. R. Samuel the son of Nahmani said: Abraham observed the laws regarding the preparation of Sabbath meals on a holy day that occurred on a Friday,¹⁹See above, n. 2. as it is said: Because that Abraham hearkened to My voice. The Holy One, blessed be He, told Abraham: Because, you devoted yourself to My law, I assure you I will be a shield unto you. Even as the shield wards off the sword and diverts the stones and arrows hurled against it, so will I shield you. Not you alone, but your descendants as well, if they devote themselves to My laws as you did. Hence it is said: The word of the Lord is tried; He is a shield unto all them who take refuge in Him (II Sam. 22:31). And it is also said: He is a shield to them that walk in integrity (Prov. 2:7).