Talmud zu Bereschit 43:3

Who disagrees?⁴⁸With the criterion of three stars for the start of night. Rebbi Ḥanina the Colleague of the Rabbis⁴⁹He usually goes by the name of R. Ḥananiah the Colleague of the Rabbis, a Babylonian who was an important teacher of the leaders of the fourth generation of Amoraim but who never headed a talmudic academy. He insists that it is logical to assert that as long as three stars can still be seen at dawn it is night even though it is relatively light and (Mishnah 5) one may well distinguish between dark blue and white, or between dark blue and dark green. Hence, since the theory of the three stars contradicts the Mishnah it must be invalid. asked: Just as you say in the evening that it is night if three stars are visible even though the sun is in the middle of the sky it is night, so you must say the same thing in the morning. Rebbi Abba⁵⁰R. Abba also was a Babylonian, a student of Rav Huna and Rav Yehudah in Babylonia, who went to Israel and became a rich silk merchant and talmudic authority of the third generation of Amoraim, a contemporary of R. Ḥanina the Colleague of the Rabbis. His argument parallels the previous one but, since it is based on Biblical verses, it seems to be an attack on the Mishnah which gives different treatments to dawn and dusk.
The first verse asserts that Lot came to Zoar at sunrise. The second verse asserts that the Cohen who had cleansed himself from impurity is purified at nightfall as explained earlier. The argument seems to center on the ambiguous statement “the sun will come and he will be pure.” Everywhere, the “coming” of the sun is its going, sundown or nightfall. In the first verse, the coming of Lot to Zoar is real coming, parallel to the going out of the sun. Hence, in the first verse coming and going out are the same. It would follow that, in the second verse also, coming must have the same status as going out since it is one of the principles of Rabbinic interpretation that Biblical expressions have the same meaning at every occurrence (a principle known as gĕzērāh šāwāh.) Hence, the different treatment of dawn and dusk in the Mishnah seems to contradict the principles of Rabbinic Bible interpretation. said: It is written (Gen. 19:23): “The sun went out over the earth and Lot came to Zoar.” And it is written (Lev. 22:7): “The sun will come and he shall be pure.” He brackets going out and coming. Since coming means that it is hidden from the creatures so also its coming out when it will be ascertained by the creatures. Rebbi Abba⁵¹It is not known if this Rebbi Abba, solving the puzzle, is the same as the author of the preceding question or another sage of the same name. The editorial principle of the Babli, to quote an authority the first time as פלוני אמר and the following times as אמר פלוני or ואמר פלוני does not apply to the Yerushalmi. said, it is written (Gen. 43:3): “In the morning it was light.” The Torah called the light morning.⁵²The Biblical text tells of Joseph’s brothers leaving Egypt to return to Canaan. Hence, it means the first dawn which was the first possible time for their leaving, and the Biblical verse connects the technical meaning of “morning” with the first light of dawn. Hence, the asymmetry of treating dawn and dusk is Biblical and Rebbi Ḥanina’s and Rebbi Abba’s arguments are unjustified. Rebbi Ismael⁵³He is a Tanna, an older contemporary of Rebbi Akiba and head of his own school. The sentence is a quote from an anonymous statement in Mekhilta dĕRibbi Ishmaël, Bo, 6): “ ‘They shall eat the meat during that night’; from here I understand during the entire night. The verse says ‘do not leave any leftovers until morning; but anything left over until morning you shall burn in fire.’ Why does the verse repeat ‘until morning’? To give a domain to the earliest part of morning. From here they said (Mishnah 3–4): ‘The consumption of the Passover sacrifice and all other sacrifices, the burning of their parts on the altar can be done until the start of dawn and all sacrifices that must be eaten within one day can be eaten until the start of dawn.’ Why did the Sages decree (that all must be done) until midnight? To remove people from transgression and to make a fence around the Torah.”
This is an additional indication that the earliest possible sign of dawn is the Biblical start of a new day. stated: (Ex. 12:10) “In the morning, in the morning,” to give a domain to the very early morning.