1) AN ERROR IN THE KIDUSHIN FOR THE WOMAN'S BENEFIT
QUESTION: The Mishnah (48b) discusses the case of a man who is Mekadesh a woman with an object which is not the same object he said it was (for example, he said, "Be Mekudeshes to me with this cup of wine," and it turned out to be a cup of honey). The Rabanan rule that she is not Mekudeshes. Rebbi Shimon rules that if the error was beneficial ("l'Shevach"), she is Mekudeshes.
Ula says that the only case of error in which Rebbi Shimon rules that the woman is Mekudeshes is an error which concerns a monetary matter (for example, the object he gave her turned out to be worth more than he said it was worth). When the error concerns a matter of lineage, "Yuchsin" (for example, he married her on condition that he was a Levi and he turned out to be a Kohen), she is not Mekudeshes because a more "Meyuchas" husband is not beneficial to her (see Rashi).
Rav Ashi cites proof for Ula's statement from the Mishnah later (49b) which teaches that if a man is Mekadesh a woman on condition that he is a Levi and he turns out to be a Kohen, she is not Mekudeshes. From the fact that the Mishnah quotes no opposing view it is clear that in a case of an error of lineage, Rebbi Shimon agrees that the woman is not Mekudeshes even when the error is to her benefit.
Mar bar Rav Ashi challenges Rav Ashi's proof from the same Mishnah. The Mishnah also teaches that if a man is Mekadesh a woman on condition that he does not have a grown daughter ("Bas Megudeles") or a Shifchah and it turns out that he has one, she is not Mekudeshes. The error in that case is one of a monetary matter which is to the woman's benefit (because if he indeed has a daughter or a Shifchah, the woman gains by having someone to serve her), and yet the Mishnah does not mention Rebbi Shimon's opposing view that she is Mekudeshes in such a case. The reason why the Mishnah does not mention his opinion is that it already mentioned his opinion in the first case of the Mishnah (on 48b). Similarly, Rebbi Shimon also disagrees in the case of the error regarding lineage, and the reason why the Mishnah omits mention of his opinion is that it has already mentioned his opinion in its first case.
The Gemara defends Rav Ashi's proof and says that one cannot assume that Rebbi Shimon disagrees in a case of an error of lineage just because he disagrees in a case of an error in monetary value. If he indeed disagrees in the case of lineage, the Mishnah (49b) should say so explicitly.
The Gemara suggests another answer and says that the "Bas Megudeles" does not refer to a grown daughter or Shifchah who can serve the woman (and is thus a monetary benefit, "Shevach Mamon," to her), but rather to an important daughter or Shifchah, who is a benefit to the woman's lineage ("Shevach Yuchsin"), and that is why Rebbi Shimon agrees in that case.
How does the Gemara's second answer explain the other cases in the Mishnah which do not refer to errors in lineage? In one case, the man is Mekadesh the woman on condition that he is a "Ben Krach" (a resident of a large city) and it turns out that he is a "Ben Ir" (a resident of a small city), or vice versa. In the other case, the man says that he has children and it turns out that he does not have children, or vice versa. These two cases are not errors of "Yuchsin" and yet the Mishnah does not mention that Rebbi Shimon disagrees.
ANSWER: The MAHARSHA (on the Mishnah) explains that although these two cases are cases of "Shevach Mamon" and not "Shevach Yuchsin," Rebbi Shimon's reason for concurrence in cases of "Shevach Yuchsin" applies to these two cases as well. Rebbi Shimon maintains that whenever the mistake is to the woman's benefit, the woman's lack of knowledge and consent (Da'as) is not an impediment to the Kidushin. The reason why an error in "Yuchsin" is different is that there is no objective preference or advantage in one over the other (Levi or Kohen); the benefit of being married to a man with a particular type of lineage is a subjective issue that depends on the preference of the woman. Therefore, it is always judged as an actual "Ta'us," error, for which it is assumed the woman did not have Da'as. The same reasoning applies to the abovementioned cases in the Mishnah. There is no clear advantage of one over the other (Ben Krach or Ben Ir, and Yesh Lo Vanim or Ein Lo), and therefore Rebbi Shimon agrees that in those cases the woman is not Mekudeshes.
(The Maharsha points out that Rashi on the Mishnah gives a different explanation. The Maharsha questions Rashi's explanation and gives a different approach to answer it.)

49b----------------------------------------49b

2) AGADAH: TEN "KAVIM" OF ARROGANCE
The Gemara relates that ten Kavim of arrogance descended to the world. Nine of them were taken by the nation of Eilam, and the remaining Kav was taken by the rest of the world. The Gemara asks that the prophet relates that Bavel received an inordinate amount of arrogance (Zecharyah 5:9-11). The Gemara answers that the arrogance first went to Bavel and from there it moved on to Eilam.
The Gemara asks that this implies that Bavel no longer has an inordinate amount of arrogance. However, it was taught that a sign of arrogance is poverty, and there is much poverty in Bavel (as the Gemara earlier mentions). The Gemara answers that the sign of arrogance is poverty of Torah, since the arrogant cannot succeed in learning Torah, while the poverty in Bavel is merely economic indigence.
RAV CHAIM OF VOLOZHEN (in RU'ACH CHAIM 1:1) points out that when the Torah describes the greatness of Moshe Rabeinu, it does not refer to his attribute of clinging (Deveikus) to Hash-m or to his attainment of great heights in spirituality. Rather, the Torah's description of Moshe states that "the man, Moshe, was exceedingly humble, more than any person on the face of the earth" (Bamidbar 12:3).
Rav Chaim explains that Moshe Rabeinu's modesty was the primary source of all of his attributes, particularly his greatness in Torah and in prophecy. A person is like a vessel: the thicker the walls, the less it can contain, and the thinner the walls, the more it can contain. A person is a vessel made to receive Torah and spirituality. The thinner he makes the "walls" of his personality, the greater and fuller a vessel he will become.
Rav Chaim adds that it is clear to him that if a person today would reach the same degree of modesty that Moshe Rabeinu reached, he would merit to receive and understand the Torah in its entirety.
3) ONE WHO SOLD HIS PROPERTY WITH INTENTION TO MOVE TO ERETZ YISRAEL
QUESTION: The Gemara discusses the case of a person who sold his property with intention to move to Eretz Yisrael but did not specify his intention at the time of the sale. Later, his plans to move changed. Rava rules that "Devarim sheb'Lev Einam Devarim" and he is bound to honor the terms of the sale.
RASHI (DH l'Nichsei) explains that the "property" which the person sold was his land (Karka).
Why does Rashi limit the case to Karka? The same Halachah should apply regardless of the type of property the person sold. Even if he sold Metaltelin (mobile property), the sale should be final.
ANSWERS:
(a) The ROSH explains the words of Rashi based on a practical consideration. Although a person might sell his belongings at any time because he is short of cash, he will not leave himself without land on which to live or to work, for he wants to retain a steady source of income. Accordingly, the claim of "Mekach Ta'us" in this case can apply only to land, in which case it is understandable that a person would sell his land only if he plans to move away. The same claim would not be accepted for Metaltelin, since it is reasonable to assume that a person sells his Metaltelin whether or not he plans to move because his Metaltelin is not so necessary to his welfare.
(b) The MAHARSHA explains the words of Rashi based on the principle of "Chezkas Mamon." In the case the Gemara discusses, the buyer took physical possession of the property before the seller's claim arose. (This necessarily must be the case, because if the buyer has not yet taken possession, the seller legally may retract the sale even if no condition or intention to such effect was present at the time of the original Kinyan. Moreover, when no money has been transferred yet, the seller is not even subject to the curse of "Mi she'Para.") The Gemara later (50a) states that even if "Devarim sheb'Lev" are considered "Devarim," they are "Devarim" only insofar as they create a doubt (Safek) as to what his original intentions were; the "Devarim sheb'Lev" do not establish his intentions beyond a doubt (Vadai).
Accordingly, there is a difference between land and Metaltelin. When a doubt arises about the ownership of an object, the rule of Chazakah dictates that the object be left in the possession of the person who is presently holding it. Land always remains in the possession of the original owner, and thus when a doubt arises it should return to the original owner, as the Gemara states. An object of Metaltelin, in contrast, is in the possession of the person who is physically holding it. Hence, even if the seller's unspoken intentions ("Devarim sheb'Lev") are taken into consideration, they are effective enough only to create a doubt, and thus the item remains in the possession of the buyer.