Shema as a Brit

והחיות עומדות אצל כסא כבודו ואין יודעות מקום כבודו. עומדות ביראה ובאימה ברתת ובזיע ומזיעת פניהם נהר של אש מושך ויוצא לפניו, שנאמר (דניאל ז, י): "נְהַר דִּי נוּר נָגֵד וְנָפֵק מִן קֳדָמוֹהִי". שנים שרפים עומדים – אחד מימינו של הקב"ה ואחד משמאלו; שש כנפים שש כנפים לכל אחד. ואחד בשתים יכסה פניו שלא יביטו פני השכינה, ושנים מכסים רגליהם, שלא יראו פני השכינה, כדי לשכח עמידת רגל עגל, ובשתים מעופפים ומעריצים ומקדישים את שמו הגדול זה עונה וזה קורא ואומרים (ישעיהו ו, ג): "קָדוֹשׁ קָדוֹשׁ קָדוֹשׁ ה׳ צְבָאוֹת מְלֹא כָל הָאָרֶץ כְּבוֹדוֹ". והחיות עומדות אצל כבודו ואינן יודעות מקום כבודו, עונות ואומרות בכל מקום שכבודו שם "ברוך כבודו ה׳ ממקומו." וישראל גוי אחד בארץ שהם מיחדים שמו תמיד, בכל יום עונים ואומרים (דברים ו, ד): "שְׁמַע יִשְׂרָאֵל ה׳ אֱלֹקֵינוּ ה׳ אֶחָד" והוא משיב לעמו ישראל: אני ה׳ אלקיכם המציל אתכם מכל צרה.

Pirkei DeRabbi Eliezer 4:6-7

The Chajjôth stand next to the throne of His glory and they do not know the place of His glory. The Chajjôth stand in awe and dread, in fear and trembling, and from the perspiration of their faces a river of fire arises and goes forth before Him, as it is said, "A fiery stream issued and came forth from before him…"(Dan. 7:10). And the wings of Gallizur the angel, who stands next to the Chajjôth, (are spread forth) so that the fire which consumes the fire of the angels should not burn (them). Two Seraphim stand, one on His right and one on His left, each one has six wings, with twain they cover their face so as not to behold the presence of the Shekhinah, with twain they cover their feet so that they should not be seen before the presence of the Shekhinah, || so that the standing of the foot of the calf might be forgotten. With twain do they fly, praising and reverencing, and they sanctify. One answers and another calls, one calls and another answers, and they say, "Holy, Holy, Holy, is the Lord of Hosts; the whole earth is full of his glory" (Isa. 6:3). The Chajjôth stand at the side of the throne of His glory and they do not know the place of His glory; they respond and say in every place where His glory is, "Blessed be the glory of the Lord from his place" (Ezek. 3:12). Israel, a nation unique on the earth, declares daily the unity of His great Name, saying, "Hear, O Israel: the Lord is our God, the Lord is one" (Deut. 6:4). He answers His people Israel and says to them, I am the Lord your God who has delivered you from every trouble.

ראש השנה ל״ב ב:י״ד-י״ז

וְהָא ״אִם הִשְׁלִים״ קָתָנֵי, דִּיעֲבַד — אִין, לְכַתְּחִילָּה — לָא! הָכִי קָאָמַר: מַתְחִיל בַּתּוֹרָה וּמַשְׁלִים בְּנָבִיא. רַבִּי יוֹסֵי אוֹמֵר: מַשְׁלִים בַּתּוֹרָה, וְאִם הִשְׁלִים בְּנָבִיא — יָצָא. תַּנְיָא נָמֵי הָכִי, אָמַר רַבִּי אֶלְעָזָר בְּרַבִּי יוֹסֵי: ווֹתִיקִין הָיוּ מַשְׁלִימִין אוֹתָהּ בַּתּוֹרָה. בִּשְׁלָמָא זִכְרוֹנוֹת וְשׁוֹפָרוֹת אִיכָּא טוּבָא, אֶלָּא מַלְכִיּוֹת — תְּלָת הוּא דְּהָוְיָין: ״ה׳ אֱלֹקָיו עִמּוֹ וּתְרוּעַת מֶלֶךְ בּוֹ״, ״וַיְהִי בִּישׁוּרוּן מֶלֶךְ״, ״ה׳ יִמְלוֹךְ לְעוֹלָם וָעֶד״, וַאֲנַן בָּעֵינַן עֶשֶׂר, וְלֵיכָּא! אָמַר רַב הוּנָא, תָּא שְׁמַע: ״שְׁמַע יִשְׂרָאֵל ה׳ אֱלֹקֵינוּ ה׳ אֶחָד״ — מַלְכוּת, דִּבְרֵי רַבִּי יוֹסֵי. רַבִּי יְהוּדָה אוֹמֵר: אֵינָהּ מַלְכוּת. ״וְיָדַעְתָּ הַיּוֹם וַהֲשֵׁבוֹתָ אֶל לְבָבֶךָ כִּי ה׳ הוּא הָאֱלֹקִים אֵין עוֹד״ — מַלְכוּת, דִּבְרֵי רַבִּי יוֹסֵי. רַבִּי יְהוּדָה אוֹמֵר: אֵינָהּ מַלְכוּת. ״אַתָּה הׇרְאֵתָ לָדַעַת כִּי ה׳ הוּא הָאֱלֹקִים אֵין עוֹד מִלְבַדּוֹ״ — מַלְכוּת, דִּבְרֵי רַבִּי יוֹסֵי. רַבִּי יְהוּדָה אוֹמֵר: אֵינָהּ מַלְכוּת.

Rosh Hashanah 32b:14-17

The Gemara raises a difficulty. Doesn’t the mishna teach: If he concluded? This indicates that after the fact, yes, one has fulfilled his obligation; ab initio, no, he has not fulfilled his obligation. The Gemara answers that this is what the mishna is saying: One begins with verses from the Torah and concludes with a single verse from the Prophets. Rabbi Yosei says: One concludes with a single verse from the Torah, and if he concluded with a single verse from the Prophets he has fulfilled his obligation. This is also taught in a baraita. Rabbi Elazar, son of Rabbi Yosei, said: Pious individuals [vatikin], who were scrupulous in their performance of mitzvot, would conclude the series with a single verse from the Torah. Presumably, Rabbi Elazar followed the opinion of his father, Rabbi Yosei. The Gemara asks: Granted, it is possible to conclude Remembrances and Shofarot with a verse from the Torah, as there are many such verses. However, with regard to Kingship, there are only three: “The Lord his God is with him, and the sounding of a king is among them” (Numbers 23:21); “And he was king in Jeshurun” (Deuteronomy 33:5); and: “The Lord shall reign for ever and ever” (Exodus 15:18). And we require ten verses, and according to Rabbi Yosei there are not enough, as he maintains that one should recite four verses from the Torah, the first three and the concluding one. Rav Huna said: Come and hear a solution from that which was taught in the Tosefta (2:11): The verse: “Hear, O Israel, the Lord our God, the Lord is one” (Deuteronomy 6:4), is a verse of Kingship; this is the statement of Rabbi Yosei. Rabbi Yehuda says: It is not a verse of Kingship. “Know this day, and lay it to your heart, that the Lord, He is God in heaven above, and upon the earth beneath; there is none else” (Deuteronomy 4:39), is a verse of Kingship; this is the statement of Rabbi Yosei. Rabbi Yehuda says: It is not a verse of Kingship. “To you it was shown, that you might know that the Lord, He is God; there is none else beside Him” (Deuteronomy 4:35), is a verse of Kingship; this is the statement of Rabbi Yosei. Rabbi Yehuda says: It is not a verse of Kingship. This shows that according to the opinion of Rabbi Yosei there are sufficient verses of Kingship in the Torah to recite three at the beginning and one at the end.

Shema can be understood as a marriage contract.
Mesechet Brachot explains that the Shema fulfills קַבּלת עֹל מַלְכוּת שָׁמַֽיִם. A קַבּלה is accepting upon oneself verbally to commit to an action. The ideological acceptance of the obligation of the yoke of heaven means that Hashem is our G-d, and there is none else.
A married couple invests themselves in the relationship's totality (emotionally, spiritually, and materially). Reaccepting the marriage contract daily, every evening and morning, when coming and going, and wearing it on one's arm and head ensures the relationship's fidelity and vitality. Midrash Zuta on Shir HaShirim 8:6, שִׂימֵ֨נִי כַֽחוֹתָ֜ם עַל־לִבֶּ֗ךָ כַּֽחוֹתָם֙ עַל־זְרוֹעֶ֔ךָ, the seal on your heart and hand refers to the tefillin worn on the hand. (See Chagai 2:23; וְשַׂמְתִּ֖יךָ כַּֽחוֹתָ֑ם כִּֽי־בְךָ֣ בָחַ֔רְתִּי נְאֻ֖ם ה׳ צְבָאֽוֹת׃). Presumably, G-d's signet would have a letter shin (The three wrappings around the finger are a signet ring that, when impressed, is reversible/invertible.).
The first paragraph specifies that the foundation is to love G-d in totality (emotionally, spiritually, and materially). How? Through His commandments. Just as a wife needs to have her ketubah imminently accessible and its contents fluent to her, this contract is spoken of at all times, whether coming or going, prominently placed in the house and worn on the arm and head.

סידור אשכנז, ימי חול, תפילת שחרית, ברכות קריאת שמע, שמע ג׳-ו׳

שְׁמַע יִשְׂרָאֵל ה׳ אֱלֹקֵֽינוּ ה׳ אֶחָד: יש להפסיק מעט בין אחד לברוך כי עיקר קבול עול מלכות שמים היא פסוק ראשון. ויאמר בלחש: בָּרוּךְ שֵׁם כְּבוֹד מַלְכוּתוֹ לְעוֹלָם וָעֶד: וְאָהַבְתָּ אֵת ה׳ אֱלֹקֶֽיךָ בְּכָל֯־לְ֯בָבְ֒ךָ וּבְכָל־נַפְשְׁ֒ךָ וּבְכָל־מְאֹדֶֽךָ: וְהָיוּ הַדְּ֒בָרִים הָאֵֽלֶּה אֲשֶׁר֯ אָ֯נֹכִי מְצַוְּ֒ךָ הַיּוֹם עַל֯־לְ֯בָבֶֽךָ: וְשִׁנַּנְתָּם לְבָנֶֽיךָ וְדִבַּרְתָּ בָּם בְּשִׁבְתְּ֒ךָ בְּבֵיתֶֽךָ וּבְלֶכְתְּ֒ךָ בַדֶּֽרֶךְ וּבְשָׁכְבְּ֒ךָ וּבְקוּמֶֽךָ: וּקְשַׁרְתָּם לְאוֹת עַל֯־יָ֯דֶֽךָ וְהָיוּ לְטֹטָפֹת בֵּין עֵינֶֽיךָ: וּכְתַבְתָּם עַל־מְזֻזוֹת בֵּיתֶֽךָ וּבִשְׁעָרֶֽיךָ:

Siddur Ashkenaz, Weekday, Shacharit, Blessings of the Shema, Shema 3-6

Hear, Israel: Adonoy is our God, Adonoy is One. The following two lines are to be said silently: Blessed [is His] Name, Whose glorious kingdom is forever and ever. And you shall love Adonoy your God with all your heart and with all your soul and with all your possessions. And these words which I command you today, shall be upon your heart. And you shall teach them sharply to your children. And you shall discuss them when you sit in your house, and when you travel on the road, and when you lie down and when you rise. And you shall bind them for a sign upon your hand, and they shall be for totafos between your eyes. And you shall write them upon the doorposts of your house and upon your gateways.

The second paragraph outlines the conditions, tanaim, of the contract. If you follow your obligations and love me, then I will provide sustenance.
Be forewarned that failure to maintain your obligation to love me, by turning your hearts and serving other G-d, thereby igniting G-d's anger in you, then my sustaining you will cease, and you will be evicted from the house that I provided for you.
This contract should be placed on your hearts, tied to your arms and head, passed to your children, and spoken about at all times and when coming home and leaving so that you will continue to live in my house as I committed to your forefathers.

סידור אשכנז, ימי חול, תפילת שחרית, ברכות קריאת שמע, שמע ז׳

(ז) וְהָיָה אִם־שָׁמֹֽעַ תִּשְׁמְ֒עוּ אֶל־מִצְוֹתַי אֲשֶׁר֯ אָ֯נֹכִי מְצַוֶּה אֶתְכֶם הַיּוֹם לְאַהֲבָה אֶת־ה׳ אֱלֹקֵיכֶם וּלְעָבְדוֹ בְּכָל֯־לְ֯בַבְכֶם וּבְכָל־נַפְשְׁ֒כֶם: וְנָתַתִּי מְטַר֯־אַ֯רְצְ֒כֶם בְּעִתּוֹ֯ י֯וֹרֶה וּמַלְקוֹשׁ וְאָסַפְתָּ דְגָנֶֽךָ וְתִירשְׁ֒ךָ וְיִצְהָרֶֽךָ: וְנָתַתִּי עֵֽשֶׂב֯ בְּ֯שָׂדְ֒ךָ לִבְהֶמְתֶּֽךָ וְאָכַלְתָּ וְשָׂבָֽעְתָּ: הִשָּׁמְ֒רוּ לָכֶם פֶּן֯־יִ֯פְתֶּה לְבַבְכֶם וְסַרְתֶּם וַעֲבַדְתֶּם אֱלֹקִים֯ אֲ֯חֵרִים וְהִשְׁתַּחֲוִיתֶם לָהֶם: וְחָרָה אַף־ה׳ בָּכֶם וְעָצַר֯ אֶ֯ת־הַשָּׁמַֽיִם וְלֹּא֯־יִ֯הְיֶה מָטָר וְהָאֲדָמָה לֹא תִתֵּן אֶת֯־יְ֯בוּלָהּ וַאֲבַדְתֶּם֯ מְ֯הֵרָה מֵעַל הָאָֽרֶץ הַטֹּבָה אֲשֶׁר֯ ה׳ נֹתֵן לָכֶם: וְשַׂמְתֶּם֯ אֶ֯ת־דְּבָרַי֯ אֵֽ֯לֶּה עַל֯־לְ֯בַבְכֶם וְעַל־נַפְשְׁ֒כֶם וּקְשַׁרְתֶּם֯ אֹ֯תָם לְאוֹת עַל֯־יֶ֯דְכֶם וְהָיוּ לְטוֹטָפֹת בֵּין עֵינֵיכֶם: וְלִמַּדְתֶּם֯ אֹ֯תָם אֶת־בְּנֵיכֶם לְדַבֵּר בָּם בְּשִׁבְתְּ֒ךָ בְּבֵיתֶֽךָ וּבְלֶכְתְּ֒ךָ בַדֶּֽרֶךְ וּבְשָׁכְבְּ֒ךָ וּבְקוּמֶֽךָ: וּכְתַבְתָּם עַל־מְזוּזוֹת בֵּיתֶֽךָ וּבִשְׁעָרֶֽיךָ: לְמַֽעַן֯ יִ֯רְבּוּ יְמֵיכֶם וִימֵי בְנֵיכֶם עַל הָאֲדָמָה אֲשֶׁר נִשְׁבַּע ה׳ לַאֲבֹתֵיכֶם לָתֵת לָהֶם כִּימֵי הַשָּׁמַֽיִם עַל־הָאָֽרֶץ:

Siddur Ashkenaz, Weekday, Shacharit, Blessings of the Shema, Shema 7

And it will be— if you vigilantly obey My commandments which I command you this day, to love Adonoy your God, and serve Him with your entire hearts and with your entire souls— that I will give rain for your land in its proper time, the early (autumn) rain and the late (spring) rain; and you will harvest your grain and your wine and your oil. And I will put grass in your fields for your cattle, and you will eat and be satisfied. Beware lest your hearts be swayed and you turn astray, and you worship alien gods and bow to them. And Adonoy’s fury will blaze among you, and He will close off the heavens and there will be no rain and the earth will not yield its produce; and you will perish swiftly from the good land which Adonoy gives you. Place these words of Mine upon your hearts and upon your souls,— and bind them for a sign upon your hands, and they shall be for totafos between your eyes. And you shall teach them to your sons, to speak them when you sit in your house, and when you travel on the road, and when you lie down and when you rise. And you shall write them upon the doorposts of your house and upon your gateways. In order that your days be prolonged, and the days of your children, upon the land which Adonoy swore to your fathers to give them [for as long] as the heavens are above the earth.

As the previous paragraph of conditions warned against diety adultery, the 3rd paragraph explains that following all commandments is a way to ensure that one will not be lured by one's eyes or heart toward infidelity. G-d concludes by stating the fulfillment of his covenant with Abraham and choosing Abraham's descendants that came from Jacob as his nation when he took them out of Egypt. "I am Hashem, your G-d who withdrew you from the land of Egypt for the purpose of being your G-d [and thereby become your spouse]. I am Hashem, your G-d.

סידור אשכנז, ימי חול, תפילת שחרית, ברכות קריאת שמע, שמע ח׳

וַֽיֹּאמֶר֯ ה׳ אֶ֯ל־משֶׁה לֵּאמֹר: דַּבֵּר֯ אֶ֯ל־בְּנֵי יִשְׂרָאֵל וְאָמַרְתָּ אֲלֵהֶם וְעָשׂוּ לָהֶם צִיצִת עַל־כַּנְפֵי בִגְ֒דֵיהֶם לְדֹרֹתָם וְנָתְ֒נוּ עַל־צִיצִת הַכָּנָף֯ פְּ֯תִיל תְּכֵֽלֶת: וְהָיָה לָכֶם לְצִיצִת וּרְאִיתֶם֯ אֹ֯תוֹ וּזְכַרְתֶּם֯ אֶ֯ת־כָּל־מִצְוֹת֯ ה׳ וַעֲשִׂיתֶם֯ אֹ֯תָם וְלֹא תָתֽוּרוּ אַחֲרֵי לְבַבְכֶם וְאַחֲרֵי עֵינֵיכֶם אֲשֶׁר֯־אַ֯תֶּם זֹנִים֯ אַ֯חֲרֵיהֶם: לְמַֽעַן תִּזְכְּ֒רוּ וַעֲשִׂיתֶם֯ אֶ֯ת־כָּל־מִצְוֹתָי וִהְיִיתֶם קְדשִׁים לֵאלֹקֵיכֶם: אֲנִי ה׳ אֱלֹהֵיכֶם֯ אֲ֯שֶׁר הוֹצֵֽאתִי אֶתְכֶם֯ מֵ֯אֶֽרֶץ מִצְרַֽיִם לִהְיוֹת לָכֶם לֵאלֹקִים֯ אֲ֯נִי ה׳ אֱלֹהֵיכֶם֯:

Siddur Ashkenaz, Weekday, Shacharit, Blessings of the Shema, Shema 8

And Adonoy spoke to Moses saying: Speak to the children of Israel, and tell them to make for themselves fringes on the corners of their garments throughout their generations; and they will place with the fringes of each corner a thread of blue. And it will be to you for fringes, and you will look upon it and you will remember all the commandments of Adonoy, and you will perform them; and you will not turn aside after your hearts and after your eyes which cause you to go astray. In order that you will remember and perform all My commandments; and you will be holy unto your God. I am Adonoy, your God, Who brought you out of the land of Egypt to be your God: I am Adonoy, your God—

Ezra headed to the Anshe Keneset H'Gedolah, so named since they restored gedolah's praise to G-d's praises, and concluded the Shema with the word emet. Yoma 49b explains that emet, truth, is the signature that G-d added to the renewal of the marriage vows between the Jewish people and G-d. Upon building the second temple, Ezra and Nechemia held a ceremony and wrote a contract to recommit the Jewish people to G-d. G-d responded with a note from descending from Heaven with the word emet. The blessing following Shema, אמת, is written six times (8 in Nusach Sephard). This is
a declaration/contract language that explains the language after אמת ויציב ... "it is true, it is binding, it is good, it is enduring...”

In the middle of the third blessing is the only none G-d reference; אַשְׁרֵי אִישׁ שֶׁיִּשְׁמַע לְמִצְוֹתֶֽיךָ וְתוֹרָתְ֒ךָ וּדְבָרְ֒ךָ יָשִׂים עַל־לִבּוֹ: "Praise worthy is the man who listens to Your commandments, and Your Torah and Your words he places on his heart."

יומא ס״ט ב:ו׳-ח׳

"וַיִּצְעֲקוּ אֶל ה׳ אֱלֹקִים בְּקוֹל גָּדוֹל״ (נחמיה ט׳:ד). מַאי אֲמוּר? אָמַר רַב, וְאִיתֵּימָא רַבִּי יוֹחָנָן: בִּיָּיא בִּיָּיא הַיְינוּ הַאי דְּאַחְרְבֵיהּ לְמַקְדְּשָׁא וְקַלְיֵהּ לְהֵיכְלֵיהּ וְקַטְלִינְהוּ לְכוּלְּהוּ צַדִּיקֵי וְאַגְלִינְהוּ לְיִשְׂרָאֵל מֵאַרְעֲהוֹן, וַעֲדַיִין מְרַקֵּד בֵּינַן. כְּלוּם יְהַבְתֵּיהּ לַן אֶלָּא לְקַבּוֹלֵי בֵּיהּ אַגְרָא? לָא אִיהוּ בָּעֵינַן, וְלָא אַגְרֵיהּ בָּעֵינַן! נְפַל לְהוּ פִּיתְקָא מֵרְקִיעָא, דַּהֲוָה כְּתִב בֵּהּ ״אֱמֶת״. אָמַר רַב חֲנִינָא: שְׁמַע מִינַּהּ חוֹתָמוֹ שֶׁל הַקָּדוֹשׁ בָּרוּךְ הוּא ״אֱמֶת״.

Yoma 69b:6-8

The Gemara recounts the event described in the verses: The verse states: And they cried with a loud voice to the Lord their God (Nehemiah 9:4). What was said? Rav said, and some say it was Rabbi Yoḥanan who said: Woe, woe. It is this, i.e., the evil inclination for idol worship, that destroyed the Temple, and burned its Sanctuary, and murdered all the righteous ones, and caused the Jewish people to be exiled from their land. And it still dances among us, i.e., it still affects us. Didn’t You give it to us solely for the purpose of our receiving reward for overcoming it? We do not want it, and we do not want its reward. We are prepared to forgo the potential rewards for overcoming the evil inclination as long as it departs from us. In response to their prayer a note fell to them from the heavens upon which was written: Truth, indicating that God accepted their request. The Gemara makes a parenthetical observation. Rav Ḥanina said: Learn from this that the seal of the Holy One, Blessed be He, is truth.