1) HALACHAH: PLANTING TREES
OPINIONS: The Mishnah (100b) discusses a case in which one person's olive trees were swept away by an overflowing river and took root in his neighbor's field. The Gemara cites a Beraisa which says that the owner of the olive trees may not remove his olive trees from his neighbor's field and replant them in his own field. Rebbi Yochanan explains that the reason for this is "Yishuv Eretz Yisrael" -- in order to settle the land of Eretz Yisrael. (Some Rishonim explain that this means that if the owner takes his trees back to his own field, the neighbor will not replant trees in his field since he did not plant any trees there in the first place, while if the owner does not take his trees back, he will plant new trees in his field, since he had planted trees there in the first place. Hence, if the owner is not permitted to take his trees back, Eretz Yisrael will be planted with more trees.) Rebbi Yochanan's reason for the ruling of the Beraisa seems to limit the ruling to Eretz Yisrael. Outside of Eretz Yisrael, however, it seems that the owner of the trees may take back his trees. Is this indeed the Halachah?
(a) Most Rishonim (see TOSFOS 101b, DH b'Sadeh) explain the Gemara in its straightforward sense, that the ruling of the Beraisa applies only in Eretz Yisrael.
(b) The RAMACH (cited by the Shitah Mekubetzes, and by the ME'IRI as "Yesh Poskin"), however, rules that this Halachah applies even outside of Eretz Yisrael. How does he understand the words, "Mishum Yishuv Eretz Yisrael"? The Ramach suggests that "Yishuv Eretz Yisrael" means the "settling of the land of a Yisrael (i.e. of a Jew)." He maintains that there is a benefit in planting and cultivating land owned by Jews even in Chutz la'Aretz. He finds a source for this in the words of Yirmeyahu to the people in exile in Bavel, "v'Dirshu Es Shelom ha'Ir..." -- "Seek the peace of the city to which I have exiled you" (Yirmeyahu 29:7). (A similar concept is expressed by the BEIS YOSEF and S'MA, CM 175:43.)
HALACHAH: The TUR and SHULCHAN ARUCH (CM 168:1) state explicitly that outside of Eretz Yisrael the owner of the trees may retrieve his trees. According to their interpretation, the ruling of the Beraisa applies only in Eretz Yisrael because of the Mitzvah of Yishuv Eretz Yisrael.
2) PAYING FOR UNSOLICITED IMPROVEMENTS MADE TO ONE'S PROPERTY
QUESTION: The Gemara discusses a case of a person who enters another person's field and plants trees without permission. Rav rules that the owner of the field is obligated to pay him, but the intruder has the "lower hand" with regard to the amount of payment. This means that if his expenses were greater than the value of the improvement he made to the field, then the owner needs to pay only the value of the improvement to the field, while if the intruder's expenses were less than the increase in the field's value, then the owner needs to pay only the expenses. Shmuel says that the owner must pay the amount that he would have paid to have trees planted in his field. Rav Papa explains that Rav and Shmuel do not argue. Rav refers to a field which was not designated to be planted, while Shmuel refers to a field which was designated to be planted.
Why should the owner of a field ever be obligated to pay for the intruder's work, which was done without permission? How can a person incur an obligation to pay for something that was done without his consent?
ANSWER: The ROSH (8:22) answers that the Gemara rules this way only in a case in which the landowner is interested in keeping the improvements made to his land. If he does not want to keep the improvements, then he indeed is entitled to tell the intruder, "Take your improvements and leave!" If he does so, of course, he is not obligated to pay.
With regard to the case of a field which was not designated to be planted, the Rosh explains that the owner claims, "I did not want these improvements to be made to my field, but since you have already made them I am willing to keep them."
The Rosh (8:23) makes a similar statement with regard to the next case in the Gemara. The Gemara discusses a case in which a person enters the destroyed building of another person and rebuilds it without permission. In such a case, there is a dispute about whether he is entitled to take away the wood and stones that he used to rebuild the other's building (or force the other to pay for them). The Rosh writes that when the following two conditions are present, the owner must pay for the renovations even if he claims that he does not want them: prior to the renovations he was not using the dilapidated building, and he is significantly financially solvent that paying for the renovations will not adversely affect his livelihood. When these two conditions are met, even if the owner claims he is not interested in the repairs, Beis Din forces him to pay, for it is assumed that he merely is trying to find a way to obtain free repairs.
The CHAZON ISH (Bava Kama 22:6) writes that Beis Din must be sensitive to the subtleties of each individual case and discern whether the property owner truly does not want the improvements made to his property, or he is just trying to obtain free labor in a devious manner while in truth he wants to make use of the work that was done. (Y. MARCUS)
3) ONE WHO FENCED-IN HIS FIELD AFTER AN INTRUDER PLANTED IT
QUESTION: The Gemara relates the incident in which Rav made his ruling concerning an intruder who plants trees in another person's field without permission. An intruder planted trees in a field without permission. The owner claimed that he did not want trees planted. Rav said that the owner must assess the improvements that the intruder made to the field and he must pay the value of either the expenses or the improvements, whichever was less. The owner refused to pay. Later, Rav saw that the owner had built a fence to protect the trees that the intruder had planted. Based on that, Rav understood that the owner was happy that they had been planted, and he forced the owner to pay the intruder the full value of the improvements (or the expenses, whichever was greater).
Why did Rav obligate him to pay? The owner explicitly expressed discontent with the improvements, and he was not obligated to accept them since the field was not designated to be planted (as Rashi points out in DH Lo Ba'ina). Even though he later built a fence around his field, that is not necessarily proof that he was satisfied that the trees had been planted. Perhaps once the trees were in his field and he could not get rid of them, he decided to build a fence to protect the field. Why, though, must he pay for the trees as if he wanted them planted there?
ANSWER: The RAMBAN explains that in the case of the Gemara, had the owner truly not desired the improvement to his field, he would have insisted that the improvement be removed rather than fence-in his field. (Y. MARCUS)
4) HALACHAH: THE PROPER WAY TO AFFIX A MEZUZAH
OPINIONS: The Mishnah lists the things that a homeowner must supply when he leases a house to a tenant, and the things that the tenant is obligated to supply. The homeowner must supply anything that requires a craftsman, while anything that does not require a craftsman is supplied by the tenant. The Gemara inquires who must supply the Mezuzah. The Gemara questions that it is obvious that the one who lives in the house is obligated to affix the Mezuzah. The Gemara answers that its initial inquiry was who must build the place in which to put the Mezuzah (such as by drilling a crevice in the doorpost). Rav Sheshes answers that since one can place the Mezuzah in a hollow reed and suspend it from the doorpost, the place of the Mezuzah does not need to be made by a craftsman and thus the tenant must provide it.
Does the Gemara here imply that a Mezuzah need not be placed directly on the doorpost, but may be placed in a case and affixed to the doorpost?
(a) The PISCHEI TESHUVAH (YD 289:2) writes in the name of the VILNA GA'ON that a Mezuzah must be placed directly on the doorpost without any case.
(b) RAV CHAIM KANIEVSKY shlit'a quotes the CHAZON ISH as having said, "These words could not have come from the [Vilna] Ga'on himself," because the Vilna Ga'on himself (in YD 289:1) cites the Gemara here as proof that a case may be used. Rav Chaim Kanievsky (in his commentary on the Rambam, Hilchos Mezuzah 2:56) suggests that the Vilna Ga'on objected only to a Mezuzah case that is made from a material different from the material from which the doorpost is made, because the case in such a situation would be a Chatzitzah between the Mezuzah and the doorpost. Accordingly, the Vilna Ga'on understood that the Gemara here refers to a case made of wood, the same material as the doorpost, and thus such a case is not a Chatzitzah ("Min b'Mino Eino Chotzetz"). (Y. MARCUS)