Halacha

הלכה א
הַמַּלְוֶה אֶת חֲבֵרוֹ וְאַחַר שֶׁהִלְוָהוּ אָמַר לוֹ אֶחָד אֲנִי עָרֵב. אוֹ שֶׁתָּבַע אֶת הַלּוֶֹה בַּדִּין וְאָמַר לוֹ אַחֵר הַנַּח וַאֲנִי עָרֵב. אוֹ שֶׁהָיָה חוֹנֵק אֶת חֲבֵרוֹ בַּשּׁוּק לִתֵּן לוֹ וְאָמַר לוֹ הַנַּח וַאֲנִי עָרֵב. אֵין הֶעָרֵב חַיָּב כְּלוּם. וַאֲפִלּוּ אָמַר אֲנִי עָרֵב בִּפְנֵי בֵּית דִּין. אֲבָל אִם קָנוּ מִיָּדוֹ שֶׁהוּא עָרֵב מָמוֹן זֶה כָּל אֵלּוּ הַפָּנִים בֵּין בִּפְנֵי בֵּית דִּין בֵּין בֵּינוֹ לְבֵין הַמַּלְוֶה נִשְׁתַּעְבֵּד:
כסף משנה
1.
The following law applies when a person gives a loan to a colleague and afterwards, a third party says: "I will act as a guarantor," the lender sues the borrower and a third party says: "Let him go. I will act as a guarantor, or the lender was strangling the borrower in the market place and a third party says: "Let him go. I will act as a guarantor." The guarantor is not obligated at all. Even if the prospective guarantor says in the presence of a court: "I will guarantee the money," he is not liable.
If, however, he formalizes his commitment to guarantee the money with a kinyan, he becomes obligated in all the above situations. This applies whether the kinyan was made in the presence of the court, or together with the lender alone.

הלכה ב
אָמַר לוֹ בִּשְׁעַת מַתַּן מָעוֹת הַלְוֵהוּ וַאֲנִי עָרֵב נִשְׁתַּעְבֵּד הֶעָרֵב וְאֵינוֹ צָרִיךְ קִנְיָן. וְכֵן אִם בֵּית דִּין עָשׂוּ אוֹתוֹ עָרֵב נִשְׁתַּעְבֵּד אַף עַל פִּי שֶׁלֹּא קָנוּ מִיָּדוֹ. כְּגוֹן שֶׁהָיוּ בֵּית דִּין רוֹצִין לִגְבּוֹת מִן הַלּוֶֹה וְאָמַר לָהֶם הַנִּיחוּהוּ וַאֲנִי עָרֵב לָכֶם הוֹאִיל וְיֵשׁ לוֹ הֲנָאָה שֶׁהֶאֱמִינוּהוּ בֵּית דִּין בְּאוֹתָהּ הֲנָיָה שִׁעְבֵּד עַצְמוֹ:
כסף משנה
2.
If, however, the guarantor told the lender when the money was being given: "Lend him, and I will be the guarantor," he becomes responsible. In such a situation, a kinyan is not necessary.
Similarly, if a court appointed him a guarantor, he becomes liable even though he did not affirm his commitment with a kinyan. For example, the court desired to expropriate property from the borrower, and this person told them: "Let him be. I will guarantee the debt for you." Since he receives satisfaction from being trusted by the court, he accepts a binding commitment upon himself.

הלכה ג
הַמַּלְוֶה אֶת חֲבֵרוֹ עַל יְדֵי עָרֵב אַף עַל פִּי שֶׁהֶעָרֵב מִשְׁתַּעְבֵּד לַמַּלְוֶה לֹא יִתְבַּע אֶת הֶעָרֵב תְּחִלָּה אֶלָּא תּוֹבֵעַ אֶת הַלּוֶֹה תְּחִלָּה. אִם לֹא נָתַן לוֹ חוֹזֵר אֵצֶל הֶעָרֵב וְנִפְרָע מִמֶּנּוּ. בַּמֶּה דְּבָרִים אֲמוּרִים בְּשֶׁאֵין נְכָסִים לַלּוֶֹה. אֲבָל אִם יֵשׁ נְכָסִים לַלּוֶֹה לֹא יִפָּרַע מִן הֶעָרֵב כְּלָל אֶלָּא מִן הַלּוֶֹה. הָיָה הַלּוֶֹה אַלָּם וְאֵין בֵּית דִּין יְכוֹלִין לְהוֹצִיא מִיָּדוֹ אוֹ שֶׁלֹּא בָּא לַדִּין הֲרֵי זֶה נִפְרָע מִן הֶעָרֵב תְּחִלָּה וְאַחַר כָּךְ יַעֲשֶׂה הֶעָרֵב דִּין עִם הַלּוֶֹה אִם יָכוֹל לְהוֹצִיאוֹ מִיָּדוֹ יוֹצִיא אוֹ יְשַׁמְּתוּהוּ בֵּית דִּין עַד שֶׁיִּתֵּן לוֹ:
כסף משנה
3.
When a person lends money to a colleague because of the commitment of a guarantor, although though the guarantor becomes responsible to the lender, the lender should not demand payment from the guarantor first. Instead, he should demand payment from the borrower first. If he does not pay him, he should return to the guarantor and collect payment from him. When does the above apply? When the borrower does not own property. If, however, the borrower does own property. He should not collect the debt from the guarantor at all. Instead, he should collect from the borrower."
If, however, the borrower is a man of force, and the court cannot expropriate money from him, or he refuses to come to the court, the lender may collect payment from the guarantor first. Afterwards, the guarantor will make a reckoning with the borrower. If the guarantor can extract payment from him, he should. If that is not possible, the court should place the borrower under a ban of ostracism until he repays the guarantor.

הלכה ד
הִתְנָה הַמַּלְוֶה עַל הֶעָרֵב וְאָמַר לוֹ עַל מְנָת שֶׁאֶפָּרַע מִמִּי שֶׁאֶרְצֶה אִם יֵשׁ נְכָסִים לַלּוֶֹה לֹא יִפָּרַע מִן הֶעָרֵב. אָמַר עַל מְנָת שֶׁאֶפָּרַע מִמִּי שֶׁאֶרְצֶה תְּחִלָּה אוֹ שֶׁהָיָה קַבְּלָן הֲרֵי זֶה יִתְבַּע אֶת הֶעָרֵב הַזֶּה אוֹ אֶת הַקַּבְּלָן תְּחִלָּה וְיִפָּרַע מֵהֶן אַף עַל פִּי שֶׁיֵּשׁ נְכָסִים לַלּוֶֹה:
כסף משנה
4.
Although the lender makes a stipulation with the guarantor and tells him: "I am giving the loan on the condition that I can collect the debt from whomever I desire," if the borrower possesses property, he should not collect the debt from the guarantor.
If he stipulated, "I am giving the loan on the condition that I can collect the debt from whomever I desire first," or the guarantor was a kablan, the lender may demand payment from this guarantor or this kablan first. He may collect payment from them although the borrower possesses property.

הלכה ה
אֵיזֶהוּ עָרֵב וְאֵיזֶהוּ קַבְּלָן. אָמַר לוֹ תֵּן לוֹ וַאֲנִי נוֹתֵן לְךָ זֶהוּ קַבְּלָן שֶׁיֵּשׁ לַמַּלְוֶה לְהִפָּרַע מִמֶּנּוּ תְּחִלָּה אַף עַל פִּי שֶׁלֹּא פֵּרֵשׁ וְלֹא אָמַר עַל מְנָת שֶׁאֶפָּרַע מִמִּי שֶׁאֶרְצֶה. אֲבָל אִם אָמַר לוֹ הַלְוֵהוּ וַאֲנִי עָרֵב הַלְוֵהוּ וַאֲנִי פּוֹרֵעַ הַלְוֵהוּ וַאֲנִי חַיָּב הַלְוֵהוּ וַאֲנִי נוֹתֵן הַלְוֵהוּ וַאֲנִי קַבְּלָן. תֵּן לוֹ וַאֲנִי קַבְּלָן תֵּן לוֹ וַאֲנִי פּוֹרֵעַ תֵּן לוֹ וַאֲנִי חַיָּב תֵּן לוֹ וַאֲנִי עָרֵב. כֻּלָּן לָשׁוֹן עַרְבָנוּת הֵן וְאֵינוֹ תּוֹבְעוֹ תְּחִלָּה וְלֹא נִפְרַע מִמֶּנּוּ בְּמָקוֹם שֶׁיֵּשׁ נְכָסִים לַלּוֶֹה עַד שֶׁיְּפָרֵשׁ וְיֹאמַר מִמִּי שֶׁאֶרְצֶה אֶפָּרַע:
כסף משנה
5.
Who is considered to be an ordinary guarantor and who is considered to be a kablan? If a person says: "Give him the loan and I will give you," he is considered to be a kablan. The lender has the option of seeking repayment from him, even though he did not explicitly stipulate: "On the condition that I can collect the debt from whomever I desire first."
If, however, he tells him: "Lend him and I will act as a guarantor," "Lend him and I will pay," "Lend him and I am obligated," "Lend him and I will give," "Lend him and I will act as a kablan" "Give him and I will act as a kablan" "Give him and I will pay," "Give him and I am obligated," or "Give him and I will serve as a guarantor" - all of these are statements that cause him to be considered a guarantor. The lender may not demand payment from him first. Nor may he collect payment from him in a situation where the lender possesses property unless he stipulates: "On the condition that I can collect... from whomever I desire first"

הלכה ו
עָרֵב שֶׁל כְּתֻבָּה אַף עַל פִּי שֶׁקָּנוּ מִיָּדוֹ פָּטוּר מִלְּשַׁלֵּם שֶׁהֲרֵי מִצְוָה עָשָׂה וְלֹא חָסַר מָמוֹן. וְאִם הָיָה הָאָב עָרֵב לִכְתֻבַּת בְּנוֹ וְקָנוּ מִיָּדוֹ חַיָּב. וְקַבְּלָן שֶׁל כְּתֻבָּה חַיָּב:
כסף משנה
6.
When a person guarantees a woman's ketubah he is not obligated to pay, even if he affirmed his commitment with a kinyan. The rationale is that he performed a mitzvah and did not cause her a financial loss. If a father guarantees his son's ketubah and affirms his commitment with a kinyan, the obligation is established. A person who becomes a kablan for a ketubah is liable.

הלכה ז
רְאוּבֵן שֶׁמָּכַר לְשִׁמְעוֹן שָׂדֶה וּבָא לֵוִי וְקִבֵּל אַחֲרָיוּת עָלָיו לֹא נִשְׁתַּעְבֵּד לֵוִי שֶׁזּוֹ אַסְמַכְתָּא הִיא. וְאִם קָנוּ מִיָּדוֹ שֶׁהוּא עָרֵב לְשַׁלֵּם דְּמֵי מֶכֶר זֶה כָּל עֵת שֶׁיִּרְצֶה שֶׁיִּתְבָּעֶנּוּ לְשִׁמְעוֹן הֲרֵי זֶה חַיָּב וְכָזֶה הוֹרוּ רַבּוֹתַי:
כסף משנה
7.
The following rules apply when Reuven sells Shimon a field and Levi accepts financial responsibility for it. Levi is not considered responsible, for this is an asmachta. If he affirmed with a kinyan his commitment to pay the money involved in this sale whenever demanded to do so by Shimon, he is obligated to do so. My masters ruled in this manner.

הלכה ח
וְכֵן הֶעָרֵב אוֹ הַקַּבְּלָן שֶׁחִיְּבוּ עַצְמָן עַל תְּנַאי אַף עַל פִּי שֶׁקָּנוּ מִיָּדוֹ לֹא נִשְׁתַּעְבֵּד מִפְּנֵי שֶׁהוּא אַסְמַכְתָּא. כֵּיצַד. כְּגוֹן שֶׁאָמַר לוֹ תֵּן לוֹ וַאֲנִי אֶתֵּן לְךָ אִם יִהְיֶה כָּךְ וְכָךְ אוֹ אִם לֹא יִהְיֶה. שֶׁכָּל הַתּוֹלֶה שִׁעְבּוּד שֶׁאֵינוֹ חַיָּב בּוֹ בְּאִם יִהְיֶה וְאִם לֹא יִהְיֶה לֹא גָּמַר וְהִקְנָה קִנְיָן שָׁלֵם וּלְפִיכָךְ לֹא נִשְׁתַּעְבֵּד:
כסף משנה
8.
Similarly, if a guarantor or a kablan make a conditional commitment, they do not become obligated even if the commitment is affirmed by a kinyan. The rationale is that this is an asmachta.
What is implied? For example, the guarantor told him: "Give him the loan and I will give you if this-and-this will take place," or "... if it will not take place." The rationale is that whenever a person undertakes an obligation for which he is personally not liable and makes it dependent on a condition: "if this takes place," or "if this does not take place," he never makes a wholehearted commitment or kinyan. Therefore, he does not become liable.

הלכה ט
שְׁנַיִם שֶׁלָּווּ בִּשְׁטָר אֶחָד אוֹ שֶׁלָּקְחוּ מִקָּח אֶחָד. וְכֵן הַשֻּׁתָּפִין שֶׁלָּוָה אֶחָד מֵהֶן אוֹ לָקַח בְּשֻׁתָּפוּת הֲרֵי הֵן עַרְבָאִין זֶה לָזֶה אַף עַל פִּי שֶׁלֹּא פֵּרֵשׁ:
כסף משנה
9.
When two people take out loans from the same person and record their debts in the same promissory note or together purchase a single article, they are considered as having guaranteed the other person's commitment even though they do not explicitly agree to do so. The same law applies when one of a group of partners undertakes a loan or makes a purchase for the partnership.

הלכה י
שְׁנַיִם שֶׁעָרְבוּ לָאֶחָד כְּשֶׁיָּבוֹא הַמַּלְוֶה לִפָּרַע מִן הֶעָרֵב יִפָּרַע מֵאֵי זֶה מֵהֶן שֶׁיִּרְצֶה. וְאִם לֹא הָיָה לְאֶחָד כְּדֵי הַחוֹב חוֹזֵר וְתוֹבֵעַ הַשֵּׁנִי בִּשְׁאָר הַחוֹב:
כסף משנה
10.
When two people both commit themselves to guarantee a debt taken on by one person, when the lender comes to collect payment from the guarantor, he may collect from either one of them, as he desires. If, however, one of them does not possess the entire amount of the debt, the lender may demand payment of the remainder from the other guarantor.

הלכה יא
וְאֶחָד שֶׁעָרַב לִשְׁנַיִם כְּשֶׁיִּפְרַע לַמַּלְוֶה יוֹדִיעוֹ עַל חוֹב אֵיזֶה מִשְּׁנֵיהֶם פּוֹרֵעַ כְּדֵי שֶׁיַּחֲזֹר עָלָיו:
כסף משנה
11.
If one person guarantees the debts of two different individuals, when a lender comes to collect payment he should tell the guarantor which of the two debts he is paying so that the guarantor will be able to seek reimbursement from the debtor.

הלכה יב
הָאוֹמֵר לַחֲבֵרוֹ עֲרֹב לִפְלוֹנִי כָּךְ וְכָךְ וַאֲנִי עָרֵב לְךָ הֲרֵי זֶה כְּמִי שֶׁאָמַר לוֹ הַלְוֵהוּ וַאֲנִי עָרֵב. וּכְשֵׁם שֶׁנִּשְׁתַּעְבֵּד הֶעָרֵב לַמַּלְוֶה כָּךְ נִשְׁתַּעְבֵּד עָרֵב לָעָרֵב רִאשׁוֹן. וְדִין הֶעָרֵב עִם הַמַּלְוֶה וְדִין עָרֵב רִאשׁוֹן עִם הַשֵּׁנִי דִּין אֶחָד הוּא:
כסף משנה
12.
When a person tells a colleague: "Guarantee a debt for so-and-so for this-and-this amount and I will guarantee the sum to you," it is as if he tells him: "Lend him the money and I will guarantee the debt." Just as the guarantor becomes obligated to the lender, the second guarantor becomes obligated to the first guarantor. The same laws that govern the relationship between the guarantor and the lender govern the relationship between the first guarantor and the second guarantor.

הלכה יג
מִי שֶׁלֹּא פֵּרֵשׁ קֶצֶב הַדָּבָר שֶׁעָרַב כְּגוֹן שֶׁאָמַר לוֹ כָּל מַה שֶּׁתִּתֵּן תֵּן לוֹ וַאֲנִי עָרֵב אוֹ מְכֹר לוֹ וַאֲנִי עָרֵב אוֹ הַלְוֵהוּ וַאֲנִי עָרֵב יֵשׁ מִן הַגְּאוֹנִים שֶׁהוֹרָה אֲפִלּוּ מָכַר לוֹ בַּעֲשֶׂרֶת אֲלָפִים אוֹ הִלְוָהוּ מֵאָה אֶלֶף נִשְׁתַּעְבֵּד הֶעָרֵב בַּכּל. וְיֵרָאֶה לִי שֶׁאֵין זֶה הֶעָרֵב חַיָּב כְּלוּם שֶׁכֵּיוָן שֶׁאֵינוֹ יוֹדֵעַ הַדָּבָר שֶׁשִּׁעְבֵּד עַצְמוֹ בּוֹ לֹא סָמְכָה דַּעְתּוֹ וְלֹא שִׁעְבֵּד עַצְמוֹ וּדְבָרִים שֶׁל טַעַם הֵם לַמֵּבִין:
כסף משנה
13.
The following opinions were stated with regard to a person who did not limit the extent of the commitment he made to serve as a guarantor. For example, he told the lender: "Give him whatever you give him, I will guarantee it," "Sell to him, and I will guarantee it," or "Lend him, and I will guarantee it."
There are Geonim who rule that even if the other person sells 10,000 zuz worth of merchandise or lends 100,000 zuz to the person named, the guarantor becomes responsible for the entire amount. It appears to me, by contrast, that the guarantor is not liable at all. Since he does not know for what he undertook the liability, he did not make a serious commitment and did not obligate himself. These are words of reason that a person of understanding will appreciate.

הלכה יד
מִי שֶׁאָמַר לַחֲבֵרוֹ הַלְוֵהוּ וַאֲנִי עָרֵב לְגוּפוֹ שֶׁל לוֶֹה זֶה לֹא עָרַב לְעַצְמוֹ שֶׁל מָמוֹן אֶלָּא כָּל זְמַן שֶׁתִּרְצֶה אֲבִיאֶנּוּ לְךָ. וְכֵן אִם אָמַר לוֹ אַחַר שֶׁהִלְוָהוּ וּתְבָעוֹ הַנִּיחֵהוּ כָּל זְמַן שֶׁתִּתְבָּעֶנּוּ אֲבִיאֶנּוּ לְךָ וְקָנוּ מִיָּדוֹ עַל זֶה אִם לֹא יָבִיא זֶה הַלּוֶֹה יֵשׁ מִן הַגְּאוֹנִים שֶׁהוֹרָה שֶׁהוּא חַיָּב לְשַׁלֵּם. וְיֵשׁ מִי שֶׁהוֹרָה שֶׁאֲפִלּוּ הִתְנָה וְאָמַר אִם לֹא אֲבִיאֶנּוּ אוֹ שֶׁמֵּת אוֹ שֶׁבָּרַח אֶהְיֶה חַיָּב לְשַׁלֵּם הֲרֵי זוֹ אַסְמַכְתָּא וְלֹא נִשְׁתַּעְבֵּד. וְלָזֶה דַּעְתִּי נוֹטָה:
כסף משנה
14.
When a person tells a colleague: "Lend him. I will guarantee the borrower's physical person," he did not make a commitment with regard to the money itself. What he meant was: Whenever you want, I will bring him to you.
Similar principles apply when, after the lender makes the loan and demands payment, a person says: "Let him go. Whenever you lodge a claim against him, I will bring him to you." If he affirms his commitment with a kinyan, there are Geonim who rule that if the guarantor does not bring the borrower to the court, the guarantor is obligated to pay. There are, however, others who rule that even if he made a stipulation saying: "If I do not bring him, or if he dies or he flees, I will be obligated to pay," the guarantor does not become liable, for this is an asmachta. I favor this understanding.

משפטים הלכות מלווה ולווה פרק כה
Mishpatim Malveh and Loveh Chapter 25