ערב שבת בין השמשות

Ten things were created on the eve of the [first] Shabbat at twilight. And these are they: The mouth of the earth [that swallowed Korach in Numbers 16:32]; and the mouth of the well [that accompanied the Israelites in the wilderness in Numbers 21:17]; and the mouth of the donkey [that spoke to Bilaam in Numbers 22:28–30]; and the rainbow [that served as a covenant after the flood in Genesis 9:13]; and the manna [that God provided the Israelites in the wilderness in Exodus 16:4–21]; and the staff [of Moshe]; and the shamir (the worm that helped build the Temple without metal tools); and the letters; and the writing; and the tablets [all of the latter three, of the Ten Commandments]. And some say, also the destructive spirits, and the burial place of Moshe, our teacher, and the ram of Abraham, our father. And some say, also the [first human-made] tongs, made with [Divine] tongs.

The Sages taught a baraita which discusses the range of problems that arise with regard to the twilight period. Twilight is a period of uncertainty. It is uncertain whether it consists of both day and night, it is uncertain whether it is completely day, and it is uncertain whether it is completely night. Therefore, the Sages impose the stringencies of both days upon it. If there is a stringency that applies on either of the days, one is obligated to adhere to it during the twilight period. Nevertheless, the definition of twilight is uncertain. And what is twilight? From when the sun sets, as long as the eastern face of the sky is reddened by the light of the sun. If the lower segment of the sky has lost its color, and the upper segment has not yet lost its color, that is the twilight period. If the upper segment has lost its color, and its color equals that of the lower one, it is night; this is the statement of Rabbi Yehuda. Rabbi Neḥemya says: The duration of the twilight period is the time it takes for a person to walk half a mil after the sun sets. Rabbi Yosei says: Twilight does not last for a quantifiable period of time; rather, it is like the blink of an eye: This, night, enters and that, day, leaves, and it is impossible to calculate it due to its brevity.