“ The school of Shammai says: In the evening all people should recline and recite [the Shema] , and in the morning they should stand, since it says [in the verse (Deut. 6:7) ] , “When you lie down and when you arise.” But the school of Hillel says: Each person may recite it in his usual way (posture) , since it says (ibid.) , “When you walk on the road.” If so, why does it say “when you lie down and when you arise”? — [It means:] at the time when people are lying down, and at the time when people are arising. ”

“ There are several approaches in the commentaries as to why Rabbi Tarfon was condemned for going beyond the letter of the law (given that the school of Hillel agrees that one may recite the Shema in the manner prescribed by the school of Shammai, just that this is not required) :
According to the school of Hillel, there is nothing at all to be gained by following the opposing opinion (since they explain the verse as not referring to bodily posture at all) . ”

“ Hebrew Text
בֵּית שַׁמַּאי אוֹמְרִים: בָּעֶרֶב כָּל אָדָם יַטּוּ וְיִקְרְאוּ, וּבַבֹּקֶר יַעַמְדוּ, שֶׁנֶּאֱמַר: "וּבְשָׁכְבְּךָ וּבְקוּמֶךָ". וּבֵית הִלֵּל אוֹמְרִים: כָּל אָדָם קוֹרֵא כְדַרְכּוֹ, שֶׁנֶּאֱמַר: "וּבְלֶכְתְּךָ בַדֶּרֶךְ". אִם כֵּן לָמָּה נֶאֱמַר "וּבְשָׁכְבְּךָ וּבְקוּמֶךָ"? בְּשָׁעָה שֶׁבְּנֵי אָדָם שׁוֹכְבִים, וּבְשָׁעָה שֶׁבְּנֵי אָדָם עוֹמְדִים. ”