Positive commandment · Mitzvat Aseh #10 of 613
To recite the Shema twice daily
לִקְרוֹת קִרְיַת שְׁמַע פַּעֲמַיִם בְּכָל יוֹם
The verse · Devarim 6:7
וְשִׁנַּנְתָּם לְבָנֶיךָ וְדִבַּרְתָּ בָּם בְּשִׁבְתְּךָ בְּבֵיתֶךָ וּבְלֶכְתְּךָ בַדֶּרֶךְ וּבְשׇׁכְבְּךָ וּבְקוּמֶךָ
“and thou shalt teach them diligently to thy children, and shalt talk of them when thou sittest in thy house, and when thou walkest by the way, and when thou liest down, and when thou risest up.”
The Rambam’s words
To recite the Shema twice daily, as [Deuteronomy 6:7] states: "And you shall speak of them when you lie down and when you arise."
לִקְרוֹת קִרְיַת שְׁמַע פַּעֲמַיִם בְּכָל יוֹם, שֶׁנֶּאֱמָר: "וְדִבַּרְתָּ בָּם בְּשִׁבְתְּךָ בְּבֵיתֶךָ וּבְלֶכְתְּךָ בַדֶּרֶךְ וּבְשָׁכְבְּךָ וּבְקוּמֶךָ" (דברים ו, ז).
Why · Sefer HaChinuch #420
Recitation of Shema morning and evening
“It is from the roots of the commandment that G-d wanted to give merit to His people that they should accept upon them His Kingdom and His unity every day and night, all the days that they are alive.”
Who & when
“And it is practiced in every place and at all times by males, but not by females; because it is in the category of positive commandments determined by time, [from which] women are exempt.”
Where in the Mishneh Torah
Hilchot Reading the Shema הלכות קריאת שמע