Halacha

הלכה א
הָאוֹמֵר לַחֲבֵרוֹ הֲנָאָה הַמְּבִיאָה לִידֵי מַאֲכָלְךָ אֲסוּרָה עָלַי. אוֹ הֲנָאָה הַמְּבִיאָה לִידֵי מַאֲכָלִי אֲסוּרָה עָלֶיךָ. הֲרֵי זֶה הַנֶּאֱסָר לֹא יִשְׁאַל מִן הָאָסוּר לוֹ נָפָה וּכְבָרָה וְרֵחַיִם וְתַנּוּר וְכָל דָּבָר שֶׁעוֹשִׂין בָּהֶן אֹכֶל נֶפֶשׁ. אֲבָל מַשְׁאִילוֹ נְזָמִים וְטַבָּעוֹת וְכֵלִים שֶׁאֵין עוֹשִׂין בָּהֶן אֹכֶל נֶפֶשׁ. וְאָסוּר לִשְׁאל מִמֶּנּוּ שַׂק לְהָבִיא בּוֹ פֵּרוֹת וַחֲמוֹר לְהָבִיא עָלָיו פֵּרוֹת:
כסף משנה
1.
When a person tells a colleague: "Benefit that leads to your food is forbidden to me," or "Benefit that leads to my food is forbidden to you," the person who is forbidden should not borrow from the other person: a sifter, a strainer, a hand mill, an oven, or any other utensil used to prepare food. He may, however, borrow from him bracelets, rings, and other articles that are not used to produce food. He is forbidden to borrow from him a sack or a donkey to carry produce.1For this also leads to him deriving pleasure from food.

הלכה ב
מָקוֹם שֶׁדַּרְכָּן שֶׁאֵין מַשְׁאִילִין כֵּלִים אֶלָּא בְּשָׂכָר. אָסוּר לִשְׁאל מִמֶּנּוּ אַף כֵּלִים שֶׁאֵין עוֹשִׂין בָּהֶן אֹכֶל נֶפֶשׁ. הֲרֵי שֶׁהָיוּ בְּמָקוֹם שֶׁאֵין נוֹטְלִין שָׂכָר וְשָׁאַל מִמֶּנּוּ כֵּלִים שֶׁאֵין עוֹשִׂין בָּהֶן אֹכֶל נֶפֶשׁ כְּדֵי לְהֵרָאוֹת בָּהֶן בִּפְנֵי אֲחֵרִים עַד שֶׁיֵּהָנֶה מֵהֶם. אוֹ שֶׁבִּקֵּשׁ לַעֲבֹר בְּאַרְצוֹ כְּדֵי שֶׁיֵּלֵךְ בְּמָקוֹם שֶׁיֵּהָנֶה בּוֹ הֲרֵי זֶה אָסוּר מִסָּפֵק. לְפִיכָךְ אִם עָבַר אֵינוֹ לוֹקֶה:
כסף משנה
2.
[In the above situation,] in a place where utensils are given out only for a fee, it is forbidden to borrow [without charge] even utensils that are not used to produce food.2For the money that he saved by not paying the fee could be used to purchase food. If they were in a place where a fee is not charged and he borrowed from him utensils that are not used to produce food to look impressive to others because of them so that he will receive benefit from them3E.g., he lent him attractive clothing which created a favorable impression on others who gave him gifts as a result. or he sought to pass through his property so that he could reach a place where he would derive benefit,4To attend a feast, but not when going to his business as stated in the notes to the following halachah. there is an unresolved question whether it is prohibited.5In both cases, he did not give him direct benefit, but he did enable him to receive benefit. Therefore, if he transgresses, he is not liable for lashes.

הלכה ג
אֵין בֵּין מֻדָּר הֲנָאָה מֵחֲבֵרוֹ לְמֻדָּר מִמֶּנּוּ הֲנָיַת מַאֲכָל אֶלָּא דְּרִיסַת הָרֶגֶל וְכֵלִים שֶׁאֵין עוֹשִׂין בָּהֶן אֹכֶל נֶפֶשׁ בְּמָקוֹם שֶׁמַּשְׁאִילִין אוֹתָם שָׁם בְּחִנָּם:
כסף משנה
3.
There is no difference between one who takes a vow not to benefit from a colleague and one who takes a vow not to derive benefit that leads to food except [permission to] pass through [property]6I.e., to tend to his business. If he took a vow against benefiting from him, he may not pass through the property, for he is deriving some benefit. Nevertheless, that benefit does not lead to food. Hence, one who prohibits all benefit is forbidden, but one who forbids benefit that leads to food is permitted. If, however, he wishes to pass through his property to attend a feast, he is forbidden in all instances, as stated in the previous halachah (Radbaz). and borrowing utensils that are not used to produce food in a place where they are borrowed without charge.7This is benefit, but not benefit that leads to food.

הלכה ד
רְאוּבֵן שֶׁנֶּאֶסְרָה עָלָיו הֲנָיַת שִׁמְעוֹן בֵּין בְּנֵדֶר בֵּין בִּשְׁבוּעָה מֻתָּר לוֹ שֶׁיִּתֵּן שִׁמְעוֹן עַל יָדוֹ מַחֲצִית הַשֶּׁקֶל שֶׁרְאוּבֵן חַיָּב בָּהּ. וְכֵן פּוֹרֵעַ חוֹב שֶׁעָלָיו שֶׁהֲרֵי לֹא הִגִּיעַ לְיַד רְאוּבֵן כְּלוּם אֶלָּא מָנַע מִמֶּנּוּ הַתְּבִיעָה. וּמְנִיעַת הַתְּבִיעָה אֵינָהּ בִּכְלַל אִסּוּר הֲנָיָה. לְפִיכָךְ מֻתָּר לוֹ לָזוּן אֶת אִשְׁתּוֹ וְאֶת בָּנָיו וַעֲבָדָיו אֲפִלּוּ הַכְּנַעֲנִים. אַף עַל פִּי שֶׁהוּא חַיָּב בִּמְזוֹנוֹתָם. אֲבָל לֹא יָזוּן אֶת בְּהֶמְתּוֹ בֵּין טְמֵאָה בֵּין טְהוֹרָה שֶׁכָּל שֶׁמּוֹסִיף בִּבְשָׂרָהּ הִיא הֲנָיָה שֶׁהִגִּיעָה לְיַד רְאוּבֵן:
כסף משנה
4.
When Reuven was forbidden to benefit from Shimon, either through a vow or through an oath, Shimon may give the half-shekel which Reuven is obligated to give.8I.e., the half-shekel which every Jew is obligated to pay to the Temple treasury as his share in the communal sacrifices. See Hilchot Shekalim 1:1. Similarly, he may pay a debt that he owes. [The rationale is that] Reuven does not receive anything, all [Shimon does] is prevent a claim from being lodged against him. And preventing a claim from being lodged is not included in the prohibition against [giving] benefit.9See Hilchot Malveh ViLoveh 26:6 where the Rambam states that if "a person pays a promissory note of a colleague without that colleague's knowledge, even if it is a debt for which security was given, the borrower is not required to pay him anything. The borrower may take his security.... The other person forfeits his money. [The rationale is that] perhaps the borrower would have been able to appease the lender and have him waive the debt." Thus by paying Reuven's debt, Shimon is not considered to have given him anything.
Therefore [Shimon] may provide food for [Reuven's] wife,10See also Hilchot Ishut 12:19 which states that when a husband traveled to a distant country and left his wife without resources, if another person gives the woman money without clearly specifying that he is extending a loan to her, he forfeits his money. Even though the husband is obligated to pay for his wife's provisions, as long as a debt is not formally established, the person who pays the money has no claim upon him. his sons, and his servants, even his Canaanite servants,11The qualifier "even" is mentioned for the Canaanite servants, because it is not as great a mitzvah to sustain them as the others who are full-fledged members of the Jewish people. even though [Reuven] is obligated to provide for their sustenance. He may not, however, provide food for [Reuven's] animal, whether a kosher animal or a non-kosher one,12This applies even though the non-kosher animal may not be eaten by the Jew, he may sell it to a gentile and will receive a greater payment because of its increase in weight. for any increase in the animal's weight is benefit given to Reuven.

הלכה ה
הָיָה שִׁמְעוֹן כֹּהֵן הֲרֵי הוּא מֻתָּר לְהַקְרִיב קָרְבְּנוֹת רְאוּבֵן. שֶׁהַכֹּהֲנִים שְׁלוּחֵי שָׁמַיִם הֵם וְאֵינָם שְׁלוּחֵי בַּעַל הַקָּרְבָּן. וּמַשִּׂיא שִׁמְעוֹן בִּתּוֹ הַבּוֹגֶרֶת לִרְאוּבֵן מִדַּעְתָּהּ. אֲבָל אִם הָיְתָה נַעֲרָה שֶׁהֲרֵי עֲדַיִן הִיא בִּרְשׁוּתוֹ אָסוּר. שֶׁזֶּה כְּמוֹסֵר לוֹ שִׁפְחָה לְשַׁמְּשׁוֹ:
כסף משנה
5.
If Shimon was a priest, he is permitted to offer sacrifices brought by Reuven. [The rationale is that] the priests are agents of God and not the agents of the person bringing the sacrifice.13And thus he is not considered as having performed a favor for the person bringing the sacrifice.
Shimon may marry off his daughter who is past maturity to Reuven with her consent.14For then, she is considered as having carried out the marriage. Her father is merely acting as her agent and thus is not considered as offering Reuven benefit. If, however, she is a na'arah,15A girl between the ages of twelve and twelve and a half who has manifested signs of physical maturity (Hilchot Ishut 2:1-2). Needless to say, this applies if the girl is a minor, in which instance, her consecration is dependent entirely on her father. she is under his domain. [Hence,] it is forbidden [to marry her to him],16For at this age, she cannot marry without her father's consent, as stated in Hilchot Ishut 3:11. because this is like giving him a maid-servant to serve him.

הלכה ו
וְתוֹרֵם שִׁמְעוֹן תְּרוּמַת רְאוּבֵן וּמַפְרִישׁ לוֹ מַעַשְׂרוֹתָיו מִדַּעְתּוֹ. כֵּיצַד מִדַּעְתּוֹ. כְּגוֹן שֶׁאָמַר רְאוּבֵן כָּל הָרוֹצֶה לִתְרֹם יָבוֹא וְיִתְרֹם. אֲבָל לֹא יֹאמַר לְשִׁמְעוֹן לִתְרֹם לוֹ שֶׁהֲרֵי עוֹשֶׂה אוֹתוֹ שָׁלִיחַ וְזֶה הֲנָיָה לוֹ:
כסף משנה
6.
Shimon may separate terumah on behalf of Reuven and separate his tithes with his consent.17If, however, Reuven does not consent, the separation of the terumah is not effective (Bava Metzia 22a). What is meant by "with his consent"? For example, Reuven said: "Whoever desires to separate terumah [from my produce] may do so." He may not, however, tell Shimon to separate terumah on his behalf, for then he is making him his agent and this is [deriving] benefit from him.

הלכה ז
וּמְלַמְּדוֹ תּוֹרָה שֶׁבְּעַל פֶּה שֶׁהֲרֵי אָסוּר לִטּל עָלֶיהָ שָׂכָר. אֲבָל לֹא תּוֹרָה שֶׁבִּכְתָב שֶׁנּוֹטְלִין עָלֶיהָ שָׂכָר. וְאִם אֵין דַּרְכָּן שָׁם לִטּל שָׂכָר עַל תּוֹרָה שֶׁבִּכְתָב הֲרֵי זֶה מֻתָּר. וּבֵין כָּךְ וּבֵין כָּךְ מֻתָּר לְלַמֵּד אֶת בְּנוֹ:
כסף משנה
7.
[Shimon] may instruct [Reuven] in the Oral Law,18Since Shimon is forbidden to receive a wage from teaching Reuven, he is not giving him tangible benefit. Although he is enabling him to observe a mitzvah, the mitzvot were not given for our satisfaction (Eruvin 31a). for it is forbidden to charge a wage for teaching it.19See Hilchot Talmud Torah 1:7, 3:10 where the Rambam issues such a ruling and explains that this is derived from Deuteronomy 4:5: "Behold, I [Moses] have taught you laws and statutes, as God commanded me." On this basis, Nedarim 37a teaches that Moses was implying: "Just as I learned at no cost, so, too, you have been instructed at no cost by me. And so, too, should you teach the coming generations at no cost."
In his Commentary to the Mishnah (Nedarim 4:3), the Rambam writes:

According to our Torah, there is no way that it is permitted to take a wage for teaching any of the Torah's professions....
I am amazed at the men of stature who aroused by desire, denied the truth had wages designated for themselves for giving Torah rulings and instruction, citing flimsy support.

See also the Rambam's Commentary to the Mishnah Avot 4:7. It must, however, by noted that most authorities [see Shulchan Aruch (Yoreh De'ah 246:5) allow a teacher to charge for the time he spends teaching Torah on the basis of the principle of sechar batalah, i.e., he could have spent the time he spends teaching working at another profession which would bring him an income. He is allowed to be reimbursed for the money he loses by choosing to teach Torah instead. For this reason, the Shulchan Aruch (Yoreh De'ah 221:2) does not accept the Rambam's ruling and forbids Shimon from teaching Reuven.
The Written Law, by contrast, may not be taught by him, because a wage can be charged for teaching it.20Nedarim 37a gives two reasons why it is permitted for a teacher of young children to charge a wage for his services: a) he is not charging for teaching; he is charging for being a disciplinarian; b) he is not charging for teaching the wordings of Torah; he is charging for teaching the cantillation notes. (For at that time, there were no texts with vowels and the Written Law was studied by memorizing its chants.) The first rationale does not apply with regard to adults, but the second does. If it is not customary [in that community] to charge for instruction in the Written Law, this is permitted. Regardless of [the local custom with regard to payment], [Shimon] may teach [Reuven's] son.21A father is obligated to teach his son the Torah. Hence, by instructing Reuven's son, Shimon is freeing him of an obligation. Nevertheless, this is not considered as providing him with benefit, for teaching his son is a mitzvah. And as stated above, the mitzvot were not given for our satisfaction. Moreover, it is possible that Reuven could find another person to teach his son without charge.

הלכה ח
חָלָה רְאוּבֵן נִכְנַס שִׁמְעוֹן לְבַקְּרוֹ. וּבְמָקוֹם שֶׁנּוֹטֵל שָׂכָר מִי שֶׁיָּשַׁב עִם הַחוֹלֶה לְצֶוֶת לוֹ לֹא יֵשֵׁב שִׁמְעוֹן אֶלָּא מְבַקְּרוֹ וְעוֹמֵד. וּמֻתָּר לוֹ לְרַפְּאוֹתוֹ בְּיָדוֹ שֶׁזּוֹ מִצְוָה הִיא:
כסף משנה
8.
If Reuven becomes ill, Shimon may come and visit him.22For this is also a mitzvah. Even though the sick person derives benefit from the person's visit, the benefit is not granted him directly (see Nedarim 39a). In a place where one who sits with a person who is ill to keep him company receives a wage, Shimon should not sit with him. Instead, he should visit him and stand.23I.e., pay a short visit and leave promptly. Since sitting with the sick person is worth money in that community, it is forbidden, by doing so, he will be providing the sick person with a tangible benefit. Payment is not given for visiting while standing. Therefore, there is no prohibition against doing so. See Siftei Cohen 221:19 who writes that if he charges for his time, he may sit and pay the sick person a longer visit. He may personally give him medical treatment, for this fulfills a mitzvah.24In his Commentary to the Mishnah (Nedarim 4:4), the Rambam states that it is a mitzvah of Scriptural origin for a doctor to heal a sick person.
The Shulchan Aruch (Yoreh De'ah 221:4) states that when medical attention is given without charge, he may treat him without charge. If, however, it is customary for a doctor to charge, he must also do so.

הלכה ט
חָלְתָה בֶּהֱמַת רְאוּבֵן לֹא יְרַפֵּא אוֹתָהּ שִׁמְעוֹן. אֲבָל אוֹמֵר לוֹ עֲשֵׂה לָהּ כָּךְ וְכָךְ. וְרוֹחֵץ עִמּוֹ בְּאַמְבְּטִי גְּדוֹלָה אֲבָל לֹא בִּקְטַנָּה מִפְּנֵי שֶׁמְּהַנֵּהוּ בְּשָׁעָה שֶׁמַּגְבִּיהַּ עָלָיו הַמַּיִם. וְיָשֵׁן עִמּוֹ בַּמִּטָּה בִּימוֹת הַחַמָּה. אֲבָל לֹא בִּימוֹת הַגְּשָׁמִים מִפְּנֵי שֶׁמְּחַמְּמוֹ. וּמֵסֵב עִמּוֹ עַל הַמִּטָּה. וְאוֹכְלִין עַל שֻׁלְחָן אֶחָד. אֲבָל לֹא מִקְּעָרָה אַחַת וְלֹא מֵאֵבוּס שֶׁלִּפְנֵי הַפּוֹעֲלִים. שֶׁמָּא יַנִּיחַ שִׁמְעוֹן חֲתִיכָה אַחַת טוֹבָה וְלֹא יֹאכַל אוֹתָהּ כְּדֵי שֶׁיֹּאכַל אוֹתָהּ רְאוּבֵן אוֹ יְקָרֵב אוֹתָהּ לְפָנָיו וְנִמְצָא מְהַנֵּהוּ. וְכֵן בְּפֵרוֹת שֶׁבָּאֵבוּס. אֲבָל אִם אָכַל שִׁמְעוֹן מִקְּעָרָה שֶׁהוּא יוֹדֵעַ שֶׁכְּשֶׁיַּחֲזִירֶנָּה לְבַעַל הַבַּיִת יַחְזֹר בַּעַל הַבַּיִת וְיַנִּיחֶנָּה לִפְנֵי רְאוּבֵן הֲרֵי זֶה מֻתָּר. וְאֵין חוֹשְׁשִׁין שֶׁמָּא הִנִּיחַ נֵתַח טוֹב בִּשְׁבִילוֹ:
כסף משנה
9.
When an animal belonging to Reuven becomes ill,25In certain manuscripts and early printings of the Mishneh Torah, this clause is included as the conclusion of the previous halachah rather than at the beginning of this one. Shimon should not give it veterinary attention. He may, however, tell him: "Do such and such for it."26I.e., he may give him advice with regard to which treatments to employ, but may not treat the animal himself. The rationale is that treating a colleague's animal is not considered a mitzvah (Tosafot, Nedarim 41b). The Beit Yosef (Yoreh De'ah 221) explains that if there is no one else capable of treating the animal but Shimon, Shimon may do so, because the mitzvah of returning a lost object also includes doing what is necessary to save a colleague's livestock. The Radbaz also adds the rationale that Scriptural Law requires us to alleviate an animal's discomfort.
[Shimon] may wash with Reuven in a large bath,27For the entrance of one person into a large bath is not significant. but not in a small bath, because he gives him pleasure by raising the water over him.28And that is considered as pleasurable. He may sleep in the same bed as him in the summer,29Because the increase in warmth is not desirable. but not in the winter, because he warms him.30The more people under the same bed clothes, the greater the warmth produced. The Shulchan Aruch (Yoreh De'ah 221:5) states that this applies with regard to a small bed. If the bed is large, even in the winter, it is permitted. He may sit on the same couch as him and eat at the same table,31This alone is not enough to create suspicion that he will offer him food. but may not eat from the same plate or from the same food trough that is placed before workers. [The rationale is that we fear that] Shimon will leave a nice piece of meat and refrain from eating it so that Shimon will eat it or move it closer to him and in this way, bring him benefit.32The Meiri explains that even though the two are at odds - and for that reason one has taken a vow not to offer the other benefit - we fear that he might make such a gesture out of good manners. Similar concepts apply with regard to produce in a food trough. It is, however, permitted for Shimon to eat from a plate even though he knows that when he returns it to the host, the host will place it before Reuven. We do not fear that [Shimon] will leave a choice cut of meat for [Reuven].33The custom was that before passing the tray to another person, the host would fill it up again. Hence there would be no need for Shimon to worry about leaving a piece for Reuven [Radbaz; Shulchan Aruch (Yoreh De'ah 221:5)]. The Rama adds that if the serving plate contained a very large amount, there is no prohibition.

הלכה י
וּמֻתָּר רְאוּבֵן לִשְׁתּוֹת כּוֹס שֶׁל תַּנְחוּמִין מִיָּדוֹ שֶׁל שִׁמְעוֹן מִשֶּׁל רְאוּבֵן וְכֵן כּוֹס שֶׁל בֵּית הַמֶּרְחָץ. שֶׁאֵין בָּזֶה הֲנָיָה:
כסף משנה
10.
It is permitted for Reuven to drink a cup of comfort34It was customary to drink wine in the house of mourners to help him overcome his sorrow (see Ketubot 8b). of his own [wine] from Shimon's hand. Similarly, he may give him the cup of the bathhouse,35A cup of hot water that was provided for bathers by the owner of the bathhouse (i.e., and not one belonging to Shimon).
Nedarim 38b states that Shimon may give Reuven "the cup of peace" and advances these two interpretations for the term. The Rambam does not consider the interpretations as mutually exclusive, for the same principle - that the satisfaction Shimon gives Reuven is minimal - applies in both instances (Kessef Mishneh).
for this does not involve satisfaction.36The Ra'avad offers a different interpretation than the Rambam, explaining that the "cup of the bathhouse" is given to save the person's life, lest he dehydrate. Moreover, he explains that since the cup belongs to Reuven, there is no difficulty. And he states that giving the cup of comfort is a mitzvah.

הלכה יא
וְאָסוּר רְאוּבֵן בְּגַחַלְתּוֹ שֶׁל שִׁמְעוֹן וּמֻתָּר בְּשַׁלְהֶבֶת שֶׁלּוֹ:
כסף משנה
11.
Reuven is forbidden to use Shimon's coal, but he is permitted to use his flame.37For the coal is considered an entity of substance, while the flame is not (Siftei Cohen 221:57).

הלכה יב
הָיָה לְשִׁמְעוֹן מֶרְחָץ אוֹ בֵּית הַבַּד מֻשְׂכָּרִים בָּעִיר. אִם הָיָה לְשִׁמְעוֹן בָּהֶן תְּפִיסַת יָד כְּגוֹן שֶׁהִנִּיחַ מֵהֶן כָּל שֶׁהוּא לְעַצְמוֹ וְלֹא שְׂכָרוֹ. אֲפִלּוּ הִנִּיחַ בַּמֶּרְחָץ אַמְבְּטִי אַחַת וּבְבֵית הַבַּד עַקָּל אֶחָד. אָסוּר לִרְאוּבֵן לְהִכָּנֵס לְאוֹתָהּ מֶרְחָץ וְלִדְרֹךְ בַּגַּת. וְאִם לֹא הִנִּיחַ לְעַצְמוֹ כְּלוּם אֶלָּא שָׂכַר הַכּל הֲרֵי זֶה מֻתָּר:
כסף משנה
12.
[The following laws apply if] Shimon owned a bathhouse or an olive press that were hired out [to others] in the city. If Shimon retains a hold on them, e.g., he left a portion for himself and did not hire it out, it is forbidden for Reuven to enter that bathhouse or tread in that olive press.38Since Shimon retains a certain dimension of ownership, when Reuven makes use of it, he is still considered as benefiting from Shimon's property. [This applies] even if he retains merely one tub in the bathhouse or one press39In his Commentary to the Mishnah (Maaserot 1:7) the Rambam defines the term ekal as referring to a container made from ropes in which olives are placed and crushed. in the olive press. If he did not retain anything for himself, but rather hired it out in its entirety, it is permitted [for Reuven to enter].40Provided Shimon did not specifically forbid Reuven from entering these structures, as indicated by Halachah 14.

הלכה יג
וְאָסוּר לִרְאוּבֵן לֶאֱכל מִפֵּרוֹת שְׂדֵה שִׁמְעוֹן וַאֲפִלּוּ בַּשְּׁבִיעִית שֶׁהַכּל הֶפְקֵר. שֶׁהֲרֵי לִפְנֵי שְׁבִיעִית נָדַר. אֲבָל אִם נָדַר בַּשְּׁבִיעִית אוֹכֵל מִן הַפֵּרוֹת הַנּוֹטוֹת חוּץ לַשָּׂדֶה. אֲבָל לֹא יִכָּנֵס לַשָּׂדֶה אַף עַל פִּי שֶׁהַקַּרְקַע הֶפְקֵר. גְּזֵרָה שֶׁמָּא יִשְׁהֶה שָׁם אַחַר שֶׁיֹּאכַל. וְלֹא הִפְקִירָה אוֹתָהּ תּוֹרָה אֶלָּא כָּל זְמַן שֶׁהַפֵּרוֹת בְּתוֹכָהּ:
כסף משנה
13.
It is forbidden for Reuven to partake of the produce of Shimon's field, even during the Sabbatical year when everything is ownerless, for he took the vow before the beginning of the Sabbatical year.41And once an entity has become forbidden because of a vow, it remains forbidden. If he took the vow in the Sabbatical year itself, [Reuven] may partake of the produce that hangs outside the field.42For that is ownerless and is not affected by the vow. He may not, however, enter the field even though the land is ownerless. [This is] a decree lest he remain there after he partook of [the produce],43Although he is allowed to benefit from the produce, he is not allowed to set foot in Shimon's land, as stated in Halachah 3, and as the Rambam continues to explain. for the Torah declared [the land] ownerless only during the time the produce is found within it.

הלכה יד
בַּמֶּה דְּבָרִים אֲמוּרִים כְּשֶׁאָמַר לוֹ הֲנָיַת הַנְּכָסִים הָאֵלּוּ אֲסוּרִין עָלֶיךָ. אֲבָל אִם אָמַר לוֹ הֲנָיַת נְכָסַי אֲסוּרִין עָלֶיךָ. אוֹ שֶׁנִּשְׁבַּע רְאוּבֵן אוֹ שֶׁנָּדַר מִנִּכְסֵי שִׁמְעוֹן. כֵּיוָן שֶׁהִגִּיעָה שְׁבִיעִית אוֹכֵל מִפֵּרוֹת שָׂדֵהוּ שֶׁהֲרֵי יָצְאוּ מֵרְשׁוּת שִׁמְעוֹן. אֲבָל לֹא יִכָּנֵס לְשָׂדֵהוּ מִן הַטַּעַם שֶׁבֵּאַרְנוּ:
כסף משנה
14.
When does the above apply? When he told him: "Benefit from this property is forbidden to you."44For then, benefit from that particular field itself becomes forbidden to Reuven forever. Compare to Chapter 5, Halachah 5. If, however, [Shimon] told [Reuven]: "It is forbidden for you to benefit from my property,"45In which case, the prohibition involves only property actually owned by Shimon without applying to any particular property individually. or Reuven took an oath or a vow [prohibiting him from benefiting] from Shimon's property, when the Sabbatical year begins, he may partake of the produce of his field, for they have left Shimon's domain.46For the entrance of the Sabbatical year causes them to be considered as ownerless. Shimon cannot cause the produce to be forbidden for Reuven, for a person cannot cause food that does not belong to him to be forbidden to a colleague (Nedarim 42b). And when Reuven takes an oath or a vow not to benefit from Shimon's property, the oath or the vow does not pertain to this produce, for it does not belong to Shimon. He may not, however, enter his field for the reasons we explained [in the previous halachah].

הלכה טו
נֶאֶסְרָה עַל רְאוּבֵן הֲנָיַת מַאֲכַל שִׁמְעוֹן בִּלְבַד. אִם לִפְנֵי שְׁבִיעִית נֶאֶסְרָה בֵּין בְּנֵדֶר בֵּין בִּשְׁבוּעָה הֲרֵי זֶה יוֹרֵד לְתוֹךְ שָׂדֵהוּ אֲבָל אֵינוֹ אוֹכֵל מִפֵּרוֹתָיו. וְאִם בִּשְׁבִיעִית נֶאֶסְרָה יוֹרֵד וְאוֹכֵל מִפֵּרוֹתָיו. שֶׁאֵין פֵּרוֹת אֵלּוּ שֶׁל שִׁמְעוֹן אֶלָּא שֶׁל הֶפְקֵר הֵן:
כסף משנה
15.
[Different laws apply if] only benefiting from Shimon's food was forbidden to Reuven,47See Halachot 1 and 3. If, either because of a vow or an oath, the prohibition took effect before the Sabbatical year, he may enter his field,48Because in such a situation, he is not forbidden to enter Shimon's property. but may not eat his produce.49Since the prohibition took effect before the Sabbatical year, it continues during the Sabbatical year, as stated in Halachah 13. If the prohibition took effect in the Sabbatical year, he may enter his field and partake of his produce, for this produce does not belong to Shimon. Instead, it is ownerless.50Hence Shimon cannot cause it to be forbidden for Reuven, as above.

הלכה טז
וְאָסוּר לִרְאוּבֵן לְהַשְׁאִיל לְשִׁמְעוֹן גְּזֵרָה שֶׁמָּא יִשְׁאַל מִמֶּנּוּ וַהֲרֵי הוּא אָסוּר בַּהֲנָאָתוֹ. וְכֵן אָסוּר לְהַלְווֹתוֹ גְּזֵרָה שֶׁמָּא יִלְוֶה מִמֶּנּוּ. וְלֹא יִמְכֹּר לוֹ גְּזֵרָה שֶׁמָּא יִקַּח מִמֶּנּוּ:
כסף משנה
16.
It is forbidden for Reuven to lend [articles] to Shimon. [This is] a decree, lest he borrow from him although it is forbidden for him to benefit from him. Similarly, it is forbidden for [Reuven] to give [Shimon] a loan. [This is] a decree, lest he borrow from him.51Reuven is not receiving any benefit from lending out either his articles or his money. Nevertheless, he is forbidden lest Shimon reciprocate and that would involve receiving benefit. Similarly, he may not sell something to him. [This is] a decree, lest he buy from him.52In a sale, even though the purchaser receives an article in return for his money, the seller is considered to have benefited. For if this was not so, he would not have sold the article.

הלכה יז
נִזְדַּמְּנָה לוֹ מְלָאכָה עִמּוֹ כְּגוֹן שֶׁהָיוּ קוֹצְרִים כְּאֶחָד. עוֹשֶׂה בְּרָחוֹק מִמֶּנּוּ גְּזֵרָה שֶׁמָּא יְסַיְּעֶנּוּ. הַמַּדִּיר אֶת בְּנוֹ מִפְּנֵי שֶׁאֵינוֹ עוֹסֵק בַּתּוֹרָה וְנֶאֱסַר בַּהֲנָיַת אָבִיו. הֲרֵי הָאָב מֻתָּר לְמַלְּאוֹת לוֹ חָבִית שֶׁל מַיִם וּלְהַדְלִיק לוֹ אֶת הַנֵּר וְלִצְלוֹת לוֹ דָּג קָטָן. שֶׁאֵין כַּוָּנָתוֹ אֶלָּא לַהֲנָאָה גְּדוֹלָה וּדְבָרִים אֵלּוּ לְגַבֵּי הַבֵּן אֵינָן חֲשׁוּבִין:
כסף משנה
17.
If it happened that [Shimon] was working with [Reuven], e.g., they were harvesting together, he should work far from him. [This is] a decree, lest he help him.
When [a father] takes a vow, forbidding his son to benefit from him because the son does not occupy himself in Torah study, the father is permitted to fill up a jug of water [for his son], light a lamp [for him], or roast a small fish. For [the father's] intent was only to forbid [his son] from deriving significant pleasure and these matters are not considered important by the son.53The Ra'avad differs with the Rambam, explaining the source for this law (Nedarim 38b) in another way. The Radbaz explains that halachically, both interpretations are acceptable. The Shulchan Aruch (Yoreh De'ah 223:1) quotes the Ra'avad's interpretation, but not of the Rambam. Accordingly, the Bayit Chadash maintains that according to the Shulchan Aruch, the Rambam's interpretation is not accepted. See also Turei Zahav 223:1 and Siftei Cohen 223:1.

הלכה יח
מִי שֶׁנִּשְׁבַּע אוֹ נָדַר שֶׁלֹּא יְדַבֵּר עִם חֲבֵרוֹ הֲרֵי זֶה מֻתָּר לוֹ לִכְתֹּב בִּכְתָב וּלְדַבֵּר עִם אַחֵר וְהוּא שׁוֹמֵעַ הָעִנְיָן שֶׁיִּרְצֶה לְהַשְׁמִיעוֹ. וְכָזֶה הוֹרוּ הַגְּאוֹנִים:
כסף משנה
18.
When a person took an oath or a vow not to speak to a colleague,54See Chapter 3, Halachot 10-11, for details on how a vow of this nature must be worded for it to be effective. he may write to him55The Baer HaGolah 221:65 rules that he may not write a note specifically for that person. Instead, he should write on the wall with the intent that the person see. Others, however, do not accept this stringency. or speak to another person even though [the person whom he forbade] hears the idea he wants to communicate to him.56He may not, however, speak to the wall, for in this instance, it is obvious that he is speaking to his colleague. The Beit Yosef (Yoreh De'ah 221) is even more stringent, stating that when it is obvious that he is intending for the person to whom he is forbidden to speak to hear, he may not speak even to another colleague. The Geonim ruled in this manner.

הפלאה הלכות נדרים פרק ו
Haflaah Nedarim Chapter 6