דאמר ליה אילו לא אוניתן לא הוה מצית הדרת בך השתא דאוניתן מצית הדרת בך ותנא תונא יפות ונמצאו רעות לוקח יכול לחזור בו ולא מוכר
the buyer can say to the seller: If you had not exploited me, you would not be able to renege on the sale, and I would receive the profit. Now that you have exploited me, can you renege on the sale and benefit? And similarly, the tanna of the mishna also taught: If the seller sold him wheat while claiming that the wheat was good, and it is found to be bad, the buyer can renege on the sale. This implies that the buyer can renege but not the seller, even in a situation where the seller would want to renege on the sale, e.g., if the item became more expensive.
ואמר רב חסדא מכר לו שוה שש בחמש והוזלו ועמדו על ג' מי נתאנה מוכר מוכר יכול לחזור בו ולא לוקח דא"ל אילו לא אוניתן לא הוה מצית הדרת בך השתא מצית הדרת בך ותנא תונא רעות ונמצאו יפות מוכר יכול לחזור בו ולא לוקח
And similarly, Rav Ḥisda says: If he sold him an item that was worth six dinars for five dinars, and its price was reduced and its value now stood at three dinars, who was exploited in this case? The seller; therefore, the seller, but not the buyer, can renege on the sale. The reason is that the seller can say to him: If you had not exploited me, you would not be able to renege on the sale. Now that you have exploited me, can you renege on the sale? And similarly, the tanna of the mishna also taught: If the seller sold him bad wheat and it is found to be good, the seller can renege on the sale, but not the buyer.
מאי קא משמע לן מתני׳ היא אי ממתני' הוה אמינא דלמא דרב חסדא תרוייהו מצו הדרי בהו ומתני' הא אתא לאשמועינן דלוקח יכול לחזור בו
The Gemara asks: What is Rav Ḥisda teaching us? It is all already taught in the mishna. The Gemara answers: If the halakha were derived from the mishna alone, I would say that perhaps in the cases brought by Rav Ḥisda, both the buyer and the seller are able to renege on the sale. The reason is that this is a case of exploitation, as the item was sold for more than its value, and therefore as long the buyer can renege on the sale, the sale is not complete. Consequently, as the seller lost out as well, he can also renege on the sale. And as for the mishna, it comes to teach us that if the seller said that he is selling good wheat and it is found to be bad, the buyer can renege on the sale, as this is considered a case of exploitation.
דס"ד אמינא משום דכתיב (משלי כ, יד) רע רע יאמר הקונה:
It is necessary to teach this, as it might enter your mind to say that this is not a case of exploitation because it is written: “It is bad, it is bad, says the buyer; but when he is gone his way, then he boasts” (Proverbs 20:14). In other words, it is the usual manner of sellers to praise their merchandise, while buyers disparage it. Therefore, the mishna teaches that the buyer can renege on the sale if the item was found to be bad, and the seller can change his mind if it was found to be good.
שחמתית ונמצאת לבנה כו': אמר רב פפא מדקתני לבנה ש"מ האי שמשא סומקתי היא תדע דקא סמקא צפרא ופניא והאי דלא קא חזינן כוליה יומא נהורין הוא דלא ברי
§ The mishna teaches that if the seller said that he was selling reddish-brown [sheḥamtit] wheat and it is found to be white, both the seller and the buyer can renege on the sale. The Gemara assumes that sheḥamtit means the color of the sun [ḥama]. Therefore, Rav Pappa said: From the fact that the mishna teaches: White, in contrast to sheḥamtit, and there are two types of wheat, one white and the other red, conclude from the mishna that this sun is red, not white. Know that this is the case, as it reddens in the morning and evening. And the reason that we do not see the red color all day is because our eyesight is not strong and we cannot discern the redness of the sun.
מיתיבי (ויקרא יג, כה) ומראהו עמוק מן העור כמראה חמה עמוקה מן הצל והתם לבן הוא כמראה חמה ולא כמראה חמה כמראה חמה דעמוקה מן הצל ולא כמראה חמה דאילו התם לבן והכא אדום
The Gemara raises an objection to this claim: With regard to a verse that speaks of leprosy: “And, behold, if its appearance is deeper than the skin” (Leviticus 13:30), the Sages explain: This means that it is like the appearance of the sun, which is deeper than the shadow. But there, leprosy is white and yet it is likened to the sun. The Gemara answers: There, it means that it has an appearance like the sun in certain respects, but it is not like the appearance of the sun in all respects. It is like the appearance of the sun in that it is deeper than the shadow, and it is not entirely like the appearance of the sun, as there the leprous spot is white, and here the sun is red.
ולמאי דסליק דעתין מעיקרא הא קא סמקא צפרא ופניא בצפרא דחלפא אבי וורדי דגן עדן בפניא דחלפא אפתחא דגיהנם ואיכא דאמרי איפכא:
The Gemara asks: And according to that which entered our mind initially, that the sun is white, doesn’t it redden in the morning and evening? The Gemara answers: In the morning it becomes red as it passes over the site of the roses of the Garden of Eden, whose reflections give the light a red hue. In the evening the sun turns red because it passes over the entrance of Gehenna, whose fires redden the light. And there are those who say the opposite in explaining why the sun is red in the morning and the evening, i.e., in the morning it passes over the entrance of Gehenna, while in the evening it passes over the site of the roses of the Garden of Eden.
יין ונמצא חומץ שניהן יכולין לחזור בהן: לימא מתניתין רבי היא ולא רבנן דתניא
§ The mishna teaches: If the seller sold wine and it is found to be vinegar, both the seller and the buyer can renege on the sale. The Gemara suggests: Shall we say that the mishna is in accordance with the opinion of Rabbi Yehuda HaNasi and not in accordance with the opinion of the Rabbis? As it is taught in a baraita: