Tosefta zu Nechemja 4:15

From when do we read Shema in the evenings? “From the time when people come [home] to eat their bread on Shabbat (Sabbath) nights,” [these are] the words of Rebbi Meir. And the Chachamim (Sages) say from the time when the Kohanim (priests) are able to eat their Terumah (heave offering). A sign for this is the coming out of the stars. And even though there is no explicit proof for this matter, there is an indirect reference: “… and half of them were holding spears from the morning twilight until the coming out of the stars.” (Nehemiah 4:15)