Tractate Berakhot - Chapter 1 - Mishnah 3 ברכות פרק א׳ משנה ג׳

Bet Shammai say: in the evening every man should recline and recite [the Shema], and in the morning he should stand, as it says, “And when you lie down and when you get up” (Deuteronomy 6:7). Bet Hillel say that every man should recite in his own way, as it says, “And when you walk by the way” (ibid). Why then is it said, “And when you lies down and when you get up?” At the time when people lie down and at the time when people rise up. Rabbi Tarfon said: I was once walking by the way and I reclined to recite the Shema according to the words of Bet Shammai, and I incurred danger from robbers. They said to him: you deserved to come to harm, because you acted against the words of Bet Hillel.