Gemara

(Beraisa): If Reuven entered Shimon's field, gathered fruit, and separated Terumah without consulting Shimon, and Shimon said 'why didn't you take nicer ones?', and there are nicer fruit that Reuven did not select for the Terumah, Shimon is sincere, and the Terumah takes effect.

Ameimar, Mar Zutra and Rav Ashi came to Mari bar Isak's orchard. Mari's sharecropper put dates in front of them. Ameimar and Rav Ashi ate, but Mar Zutra did not. Mari came and asked his sharecropper 'why didn't you give them from these nice ones?'

Ameimar and Rav Ashi (to Mar Zutra): Why don't you eat now?

Mar Zutra: Rava taught that 'why didn't you take nicer ones?' applies only to Terumah, for people are happy to do Mitzvos (nicely). Here, (perhaps) Mari suggested giving nicer ones only because he was embarrassed.

Eruvin 71a (Mishnah - Beis Shamai): One (who did not make an Eruv) may give Reshus (rights to his property, only) before Shabbos;

Beis Hillel say, one may give Reshus (even) on Shabbos.

(Ula): Beis Hillel consider Bitul (giving Reshus) on Shabbos like the case of 'take nicer ones!'

Bava Kama 119a: Rava bought vine shoots from a sharecropper.

Question (Abaye - Mishnah): We may not buy fruit or wood from people who guard fruit.

Rava: The Mishnah discusses guards, who get no share of the Peros. A sharecropper gets a share; we may suppose that he sells from his share.

Kesuvos 48a (Rav Chisda): If a man went insane, Beis Din takes from his property to feed his wife and children, and for something else (this will be explained).

Question (Ravina - Beraisa): If a man went overseas and his wife demands food, Beis Din takes from his property to feed her, but not to feed his children or for something else.

Answer (Rav Ashi): One who left intentionally is unlike who left unintentionally.

(Rav Chisda): 'Something else' is cosmetics (for his wife).

(Rav Yosef): It is Tzedakah.

Rav Yosef would say that we give to her cosmetics. Her husband does not want her to become repulsive.

Rishonim

Rambam (Hilchos Terumos 4:3): If Reuven separated Terumah (from Shimon's Peros) without permission, or took Peros from Shimon's field, and separated Terumah, and.Shimon said 'why didn't you take nicer ones?', If there are nicer fruits, the Terumah takes effect.

Ketzos ha'Choshen (262:1): In Eruvin (71a), Beis Hillel hold that Bitul Reshus on Shabbos works, for it is like 'why didn't you take nicer ones?' Shlichus does not apply there; we must say that it is because it is a Mitzvah. Also, Poskim permit using another's Esrog or Sukah (Taz 637:4) because one is happy that others use his property for a Mitzvah, even though now he does not know. One may not eat another's food, even if he knows that the owner would consent if he knew, since he does not know now, and the Halachah follows Abaye. We must say that Mitzvos are different. Once, due to Ones one forgot to be Mevatel his Chametz before the sixth hour on Erev Pesach, and after six hours he remembered and was Mevatel. This is like Bitul after dark in Eruvin. It says in Pesachim (7a) that after six hours, one cannot be Mevatel. We can say that that Sugya is rejected due to the Sugya in Eruvin, just like we rejected the Sugya in Bava Metzia. I joined this to many other reasons to permit benefit from it. One cannot be Mevatel after six hours only if he knew from the beginning and was not Mevatel. (Normally, we must be stringent, for the Poskim did not distinguish.)

Rebuttal (Nesivos ha'Mishpat Bi'urim 4): Always, a person does not want the Isur of Chametz! He has no gain from it; the Torah removed it from his Reshus! Nevertheless, the Torah obligates him for it unless he was Mevatel with his mouth or in his heart.

Rosh (2:3): Even though Mari did not know that his sharecropper was giving fruits to Rabanan, and the Halachah is that Ye'ush she'Lo mi'Da'as is not Ye'ush, Rav Ashi and Ameimar relied on the sharecropper to give from his own portion, and to give to Mari others in place of what he gave. Mar Zutra would not eat before Mari divided with his sharecropper.

Hagahos Ashri (2:3) and Mordechai (425): In Bava Kama (119a), Rava said that a sharecropper brings from his own share. This is when he brings from his house. Here, Mari's sharecropper brought from the orchard. Mar Zutra feared lest he not tell Mari at the time of division.

Ramban (Bava Metzia 22a DH Ameimar): Why did Ameimar and Mar Zutra (note: the Ramban's text was different than ours) eat? A Mishnah forbids buying from people who guard fields. They did not know that Mari would come and consent! If the sharecropper owned a share of the fruits, why didn't Rav Ashi eat? Rava bought vine shoots from a sharecropper. Presumably, Rav Ashi agrees! Rav Ashi must permit only after division, but not attached Peros that were not divided yet. Ameimar and Mar Zutra held that since he owns a share, he gives his own. It suffices that he wil tell the (land) owner at the time of division. The owner himself is pleased to divide attached Peros in such a case. After Mari came, it was clear that he approved of the 'Shlichus' to divide in his absence. If we would say that they ate Mari's fruits, this is unlike the proof from Terumah! Rav Ashi was stringent, for regarding Terumah it is customary to separate generously. Here, perhaps Mari was particular to divide only after the fruits were detached!

Ran (in Shitah Mekubetzes 22a DH Ameimar): The Rashba answered that even if the sharecropper had no share in the fruits, we estimate that the owner would not mind. This is the custom. A Tosefta teaches that a son or slave eating from his father or master may give a piece to the son or slave of his friend without concern for theft, for this is the custom. This is why we may take a small amount of Tzedakah from women.

Poskim

Shulchan Aruch (358:4): One may buy from a sharecropper, for he owns a share of the Peros and wood.

Shach (1): Tosfos (22a DH Mar), Hagahos Ashri and the Mordechai say that if Ploni gives Levi's food to David, David may not eat, even if he knows that Levi would consent. The Halachah follows Abaye; consent at the end does not help for beforehand. I would distinguish. One despairs against his will because he does not know where the object is. Therefore, it came to the finder's hand b'Isur. He cannot acquire through despair, for the owner does not know now, and if he knew that the finder has it, he would not despair. Here, since David knows that Levi will not mind, it came to him b'Heter. Even though the Gemara compares Terumah and Tum'ah to Ye'ush she'Lo mi'Da'as, Terumah and Tum'ah are different, for they require proper awareness.

Maharit (1:150): In the Yerushalmi (Bava Basra, Sof Perek 2) R. Chanina was stringent not to give to R. Yochanan figs of R. Chanina's son, even though a son normally does not mind if his father takes (Nedarim 25b)

Ketzos ha'Choshen (1): In Kesuvos, Rashi explains that if one went insane, we assume that he would want Beis Din to feed his wife and children. Even when we know that one would consent, it is Ye'ush she'Lo mi'Da'as. Why may we take his property? Perhaps it is because there is a Mitzvah to feed children. Even though we do not force one to feed children above six, he is pleased to do the Mitzvah. However, we uses his money even for cosmetics (which is not a Mitzvah). Why does it suffice that he would consent?

Imrei Baruch: Bava Kama 119a permits taking a small amount of Tzedakah from a married woman. We estimate that a man would consent; Zachin l'Adam she'Lo Befanav (we may do something beneficial for someone in his absence). The same applies to one who went insane. Everyone wants to feed his family. If he were sane, he would want this!

Rema: Some say that this is only after they divided, for then we may assume that he sells his own. One may not buy before division, lest the sharecropper not give to the landowner corresponding to what he took.