Talmud for Eruvin 3:1
חמתה מרובה מצילתה בסוכה פסולה ובמבוי כשר סוכה מקורה פסולה מבוי מקורה כשר רבי אמי בשם רב הושעיא לא סוף דבר מקורה אלא נתן מלתרא יש בו רחב ארבעה טפחים מתרת את המבוי רבי אחא רבי חיננא בשם כהנא הלכה כרבי יודה דלא כן מה אנן אמרינן רבי יודה וחכמים תהא הלכה כרבי יודה אלא בגין דא"ר יעקב בר אידי בשם ר' יהושע בן לוי הלכה כדברי המיקל בהלכות עירובין ואמר רב נחמן בר יצחק בשם רבי יהושע בן לוי הלכה כרבי יוחנן בן נורי ומקשינן עליה לא כן אמר רבי יעקב בר אידי בשם רבי יהושע בן לוי הלכה כדברי המיקל בהילכות עירובין לא כן א"ר יצחק בר נחמן בשם ריב"ל הלכה כרבי יוחנן בן נורי וקשיינן עלה סברין מימר יחיד אצל יחיד הא יחיד אצל חכמים לא אתא רבי יעקב בר אחא רבי יעקב בר אידי בשם ר' יהושע בן לוי הלכה כרבי יוחנן בן נורי ואפילו חכמים החלוקין עליו וכא תהא הלכה כרבי יודה ואפילו חכמים החלוקים עליו שמואל אמר הלכה כדברי המיקל בעירובין א"ל רב חייה בר אשי כגון ההוא דתנינן תמן וכן גשרים המפולשין מטלטלין תחתיהן בשבת דברי רבי יודה וחכמים אוסרין א"ל לא עירובין אמרתי אלא מחיצות סבר כהנא כהדא דשמואל לפום כן צריך מימר אין הלכה כרבי יודה לא אמר אלא למעשה מעשרים הא בסוף עשרים כשר ותייא כרב דרב אמר
a creative task, he should bring a sin offering. Two--he should bring a conditional sin offering. Three--he is exempt [from bringing a sacrifice of any sort.]” Rabbi Yose bar Bon raised the question [thus]: “If you were to say that two [stars indicate] doubt [as to whether it is day or night, then] if one saw two stars on the eve of the Sabbath and [others] warned him [that it was the Sabbath, thus making him liable for its violation], yet he [nonetheless] performed a creative task; [and if he subsequently] saw two stars on the departure of the Sabbath and [others] warned him [that it was still the Sabbath], yet he performed a creative task; then either way you like [he is liable for a violation of the Sabbath]. If the first [set of stars] were [an indication that it was still] daytime [and not yet the Sabbath], then the last stars were also [an indication that it was still] daytime [and still the Sabbath], then he is liable [for a violation of the Sabbath] on account of the last set [of stars]. If the last [set of stars] were [an indication that it was now] night time [and the Sabbath had begun], then the first stars were also [an indication that it was now] night time [and no longer the Sabbath], then he is liable [for a violation of the Sabbath] on account of the first set [of stars]. [Another example:] If he saw two stars on the eve of the Sabbath and partially harvested a fig, [and] if he [subsequently returned] in the morning and harvested another part, and if he saw two stars on the departure of the Sabbath and harvested the [last] part of the fig, then either way you like [he is liable for a sin offering]. If the first [set of stars] were [an indication that it was still] daytime [and not yet the Sabbath], then the last stars were also [an indication that it was still] daytime [and still the Sabbath] and the morning harvest joins with that of the departure of the sabbath, and he is liable [for a sin offering] on account of the last set [of stars]. If the last [set of stars] were [an indication that it was] night time [and now the Sabbath], then the last stars were also [an indication that it was] daytime [and no longer the Sabbath] and the morning harvest joins with that of the night of the Sabbath, and he is liable [for a sin offering] on account of the first set [of stars].” These [stars] that you are speaking of are [only] those whose way is not to appear in the daytime. However, we do not count those whose way is to appear in the daytime. Rabbi Yose bar Bon said: “Just so long as three stars may be seen aside from that [one we call] Kokhvata (prob. Venus).” (This may be a scribal error and the original version may have been: “Just so long as three stars may be seen [in one place, just] as one star [can be so seen.]”) Rabbi Yaakov of Romana in the name of Rabbi Yehuda ben Pazi: “One star, surely day. Two, night.” But does he [truly] have no [time period of] doubt!? He has doubt about [discerning] one star from another. A baraita teaches: “So long as the eastern horizon is reddened, it is daytime. What has been said about the stars, applies to those which are not generally seen until nightfall; for, no note is taken of those which appear before the day is terminated. Therefore, R. Yosse bar R. Aboon says: It means three stars not counting, R. Jacob from Darom (south) says: One star indicates that it is still day; but two stars certainly show that it is night. Is there any doubt of this? No; the doubt can only exist between the stars visible by day, and the other stars. With regard to this, we are taught that it is still day as long as the sky is red towards the east;