תרי תילתי מיל מאי בינייהו איכא בינייהו פלגא דדנקא
it means two-thirds of a mil. The Gemara explains: What is the practical difference between them? The practical difference between them is half of one-sixth [danka], i.e., one-twelfth of a mil. Their disputes are consistent, as the duration of twilight according to Rav Yosef is shorter than its duration according to Rabba.
וחילופה בחלתא דאמר רבה חלתא בת תרי כורי שרי לטלטולה ובת תלתא כורי אסור לטלטולה ורב יוסף אמר בת תלתא כורי נמי שרי בת ארבעה כורי אסור
The Gemara comments: And with regard to the legal status of a wicker vessel their dispute is the opposite. In that case, the size of the vessel permitted by Rav Yosef is larger than the size of the vessel permitted by Rabba. As Rabba said with regard to a wicker vessel with a capacity of two kor, one is permitted to move it on Shabbat. And one with a capacity of three kor, one is prohibited to move it on Shabbat. It is much larger than the dimensions of a vessel and one is only permitted to move vessels on Shabbat. And Rav Yosef said: A vessel with a capacity of three kor, one is also permitted to move it, and only one with a capacity of four kor, it is prohibited to move.
אמר אביי בעי מיניה דמר בשעת מעשה ואפילו בת תרי כורי לא שרא לי כמאן כהאי תנא דתנן כוורת הקש וכוורת הקנים ובור ספינה אלכסנדרית אף על פי שיש להם שולים והן מחזיקות ארבעים סאה בלח שהן כוריים ביבש טהורים אמר אביי שמע מינה האי גודשא תילתא הוי
Abaye said: I raised the dilemma before my Master, Rabba, when it was practical, when I actually needed to know what to do, and he did not permit me to move even a vessel with a capacity of two kor. The Gemara explains: In accordance with whose opinion did Rabba issue his practical halakhic ruling? In accordance with the opinion of this tanna that we learned in the mishna discussing the laws of ritual purity: A round straw barrel, and a round barrel made of reeds, and the cistern of an Alexandrian ship, which is a large vessel placed on a boat and filled with potable water, although these vessels have bottoms, i.e., they are receptacles, since they have a capacity of forty se’a of liquid, which is the equivalent of two kor of dry goods, they are ritually pure. Even if they come into contact with a source of ritual impurity, they do not become impure. Beyond a certain size, containers are no longer considered vessels and, consequently, cannot become ritually impure. Rabba held: Since with regard to the halakhot of ritual impurity a vessel of two kor is not considered a vessel, it may not be moved on Shabbat. With regard to this mishna, Abaye said: Learn from it that the surplus of dry goods in a vessel relative to liquids is one-third of the contents of the vessel. It says in the mishna that a vessel that can hold forty se’a of liquid holds two kor of dry produce, which is the equivalent of sixty se’a.
אביי חזייה לרבא דקא דאוי למערב אמר ליה והתניא כל זמן שפני מזרח מאדימין אמר ליה מי סברת פני מזרח ממש לא פנים המאדימין את המזרח איכא דאמרי רבא חזייה לאביי דקא דאוי למזרח אמר ליה מי סברת פני מזרח ממש פנים המאדימין את המזרח וסימניך כוותא:
The Gemara relates: Abaye saw that Rava was gazing westward on Shabbat eve to determine whether or not the sky was red and whether or not it was twilight. Abaye said to Rava: Wasn’t it taught in a baraita that twilight is from when the sun sets, as long as the eastern face of the sky is reddened by the light of the sun? Why, then, are you looking westward? Rava said to him: Do you hold that the reference is actually to the eastern face of the sky? No, it is referring to the face of the sky that causes the east to redden, i.e., the west. Some say a different version of that incident. Rava saw that Abaye was gazing eastward. He said to him, do you hold that the reference is to the actual eastern face of the sky? The reference is to the face of the sky that causes the east to redden, i.e., the west. And your mnemonic is a window, as it is on the wall opposite the window that one can see how much sunlight is shining through.
רבי נחמיה אומר כדי שיהלך אדם משתשקע החמה חצי מיל: אמר רבי חנינא הרוצה לידע שיעורו של רבי נחמיה יניח חמה בראש הכרמל וירד ויטבול בים ויעלה וזהו שיעורו של רבי נחמיה
With regard to that which was taught in the baraita that Rabbi Neḥemya says: The duration of twilight is the time it takes for a person to walk half a mil after the sun sets. Rabbi Ḥanina said: One who wants to know the precise measure of Rabbi Neḥemya’s twilight should do the following: Leave the sun at the top of Mount Carmel, as when one is standing on the seashore he can still see the top of Mount Carmel in sunlight, and descend and immerse himself in the sea, and emerge, and that is Rabbi Neḥemya’s measure of the duration of twilight.
אמר רבי חייא הרוצה לראות בארה של מרים יעלה לראש הכרמל ויצפה ויראה כמין כברה בים וזו היא בארה של מרים אמר רב מעין המיטלטל טהור וזהו בארה של מרים:
Because of its similarity to Rabbi Ḥanina’s statement, the Gemara cites that which Rabbi Ḥiyya said: One who wants to see Miriam’s well, which accompanied the Jewish people throughout their sojourn in the desert, should do the following: He should climb to the top of Mount Carmel and look out, and he will see a rock that looks like a sieve in the sea, and that is Miriam’s well. Rav said: A spring that is portable, i.e., that moves from place to place, is ritually pure and is regarded as an actual spring and not as drawn water. And what is a movable spring? It is Miriam’s well.
אמר רב יהודה אמר שמואל בין השמשות דרבי יהודה כהנים טובלין בו למאן אילימא לרבי יהודה ספקא הוא אלא בין השמשות דרבי יהודה לרבי יוסי כהנים טובלין בו
Rav Yehuda said that Shmuel said: During Rabbi Yehuda’s twilight, ritually impure priests who want to immerse themselves during the day to become ritually pure, so that sunset will follow immersion and they will be permitted to eat teruma, can still immerse themselves during that period. According to this opinion, twilight is still considered to be day. The Gemara asks: In accordance with whose opinion is that true? If you say that it is in accordance with Rabbi Yehuda’s own opinion, his opinion cited above is that twilight is a period of uncertainty. Therefore, one who immerses at that time may not eat teruma until after the sunset of the following day. Rather, the reference is to twilight of Rabbi Yehuda, in accordance with the opinion of Rabbi Yosei. Priests can immerse then, as Rabbi Yosei considers that time to still be day, and sunset will follow.
פשיטא מהו דתימא בין השמשות דרבי יוסי מישך שייך בדרבי יהודה קא משמע לן דשלים בין השמשות דרבי יהודה והדר מתחיל בין השמשות דרבי יוסי
The Gemara asks: It is obvious that according to Rabbi Yosei they are immersing themselves during the day. The Gemara answers: Lest you say that the twilight of Rabbi Yosei is subsumed within and takes place at the end of the twilight of Rabbi Yehuda. When the twilight of Rabbi Yehuda ends, Rabbi Yosei’s twilight is also over. It is already night, sunset of that day has already passed, and there is no sunset to enable them to eat teruma. Therefore, he teaches us that Rabbi Yehuda’s twilight ends, and only thereafter does Rabbi Yosei’s twilight begin.
אמר רבה בר בר חנה אמר רבי יוחנן הלכה כרבי יהודה לענין שבת והלכה כרבי יוסי לענין תרומה בשלמא הלכה כרבי יהודה לענין שבת לחומרא אבל לענין תרומה מאי היא אילימא לטבילה ספקא היא
Rabba bar bar Ḥana said that Rabbi Yoḥanan said: The halakha is in accordance with the opinion of Rabbi Yehuda with regard to the matter of Shabbat, and the halakha is in accordance with the opinion of Rabbi Yosei with regard to the matter of teruma. The Gemara asks: Granted, concerning the statement that the halakha is in accordance with the opinion of Rabbi Yehuda with regard to the matter of Shabbat, as like all other cases of uncertainty, the ruling is stringent with regard to Torah prohibitions. However, with regard to teruma, what is the case under discussion? If you say that it is referring to the matter of immersion, immersion is also a case of uncertainty with regard to a Torah law. Why would the ruling be more lenient in that case than in the case of Shabbat?