The Talmud discusses the acceptance of the yoke of Heaven (kabbalat ol malkhut shamayim) during Shema, connecting the declaration of God's unity to emunah as an internalized, lived experience rather than mere intellectual assent.
רַבִּי יִרְמְיָה הֲוָה יָתֵיב קַמֵּיהּ דְּרַבִּי [חִיָּיא בַּר אַבָּא], חַזְיֵיהּ דַּהֲוָה מַאֲרֵיךְ טוּבָא, אֲמַר לֵיהּ: כֵּיוָן דְּאַמְלֵיכְתֵּיהּ לְמַעְלָה וּלְמַטָּה וּלְאַרְבַּע רוּחוֹת הַשָּׁמַיִם — תּוּ לָא צְרִיכַתְּ. תָּנוּ רַבָּנַן: ״שְׁמַע יִשְׂרָאֵל ה׳ אֱלֹהֵינוּ ה׳ אֶחָד״ זוֹ קְרִיאַת שְׁמַע שֶׁל רַבִּי יְהוּדָה הַנָּשִׂיא. אֲמַר לֵיהּ רַב לְרַבִּי חִיָּיא: לָא חֲזֵינָא לֵיהּ לְרַבִּי דִּמְקַבֵּל עֲלֵיהּ מַלְכוּת שָׁמַיִם. אֲמַר לֵיהּ: בַּר פַּחֲתֵי, בְּשָׁעָה שֶׁמַּעֲבִיר יָדָיו עַל פָּנָיו, מְקַבֵּל עָלָיו עוֹל מַלְכוּת שָׁמַיִם.
The Gemara relates that Rabbi Yirmeya was seated before Rabbi Ḥiyya bar Abba. He saw that he was greatly extending his pronunciation of eḥad. He said to him: Once you have crowned Him in your thoughts over everything above, in Heaven, below, on earth, and in the four corners of the heavens, you need not extend any further. The Sages taught in a baraita: The single verse, “Hear, Israel, the Lord is our God, the Lord is One”; this is Rabbi Yehuda HaNasi’s recitation of Shema. The Gemara relates: Rav said to his uncle, Rabbi Ḥiyya: I did not see Rabbi Yehuda HaNasi accept the kingship of Heaven upon himself, meaning that he did not see him recite Shema. Rabbi Ḥiyya said to him: Son of noblemen [bar paḥtei], when Rabbi Yehuda HaNasi passed his hands over his face in the study hall in the middle of his lesson, he accepted the yoke of the kingdom of Heaven upon himself, as his Shema was comprised of a single verse.