Eruvin 1

משנה מבוי שהוא גבוה מעשרים אמה ימעט רבי יהודה אומר אינו צריך והרחב מעשר אמות ימעט אם יש לו צורת פתח אף ע"פ שהוא רחב מעשר אמות אינו צריך למעט:

From when may one recite Shema in the evening? From the time the Kohanim go in to eat their Terumah (produce consecrated for priestly consumption). Until the end of the first watch, says Rabbi Eliezer. And the Sages say: Until [astronomical] midnight. Rabban Gamliel says: Until the break of dawn. It once happened that his [Rabban Gamliel’s] sons came from a house of feasting. They said to him: We have not recited Shema. He to them: If dawn has not broken, you are obligated to recite it. And it is not only in this case that they said it! Rather, in all cases where the Sages said "only until midnight," the obligation remains until the break of dawn. [e.g.] Burning the fats and limbs [of the sacrifices, on the Temple altar] — the obligation is until the break of dawn. [e.g.:] All [sacrifices] which may be eaten for one day — the obligation is until the break of dawn. If that is so, why did the Sages say, "until midnight?" To distance a person from transgression.

גמרא ר' יוסה אמר לה סתם רבי אחא בשם רב רבנן ילפין לה מפתחו של היכל ורבי יודה יליף לה מפתח

We recite [in our mishnah] "...from the time that the kohanim (Aaronide priests) enter to eat their Terumah (produce consecrated for priestly consumption)." Rabbi Chiya taught [in Tosefta Berakhot 1:1]: "...from the time that people usually go in to eat their bread on the eve of the Sabbath." And there is a baraita that comments on this: "These opinions are close enough to be equal."