Bava Batra 173B

ואם אמר לו: ״על מנת שאפרע ממי שארצה״⁠ – יפרע מן הערב. רבן שמעון בן גמליאל אומר: אם יש נכסים ללוה ⁠– בין כך ובין כך לא יפרע מן הערב.

But if the creditor said to the debtor: I am lending the money on the condition that I will collect the debt from whomever I wish, i.e., either the debtor or the guarantor, he can collect the debt from the guarantor. Rabban Shimon ben Gamliel says: If the debtor has property of his own, then whether in this case, where the creditor stipulated this condition, or that case, where he did not, he cannot collect the debt from the guarantor.

וכן היה רבן שמעון בן גמליאל אומר: הערב לאשה בכתובתה, והיה בעלה מגרשה ⁠– ידירנה הנאה; שמא יעשו קנוניא על נכסים של זה, ויחזיר את אשתו.

And so Rabban Shimon ben Gamliel would say: If there is a guarantor for a woman for her marriage contract, from whom the woman can collect payment of her marriage contract instead of collecting it from the husband, and her husband was divorcing her, the husband must take a vow prohibiting himself from deriving any benefit from her, so that he can never remarry her. This precaution is taken lest the couple collude [kenunya] to divorce in order to collect payment of the marriage contract from this guarantor’s property, and then the husband will remarry his wife.

גמ׳ מאי טעמא? רבה ורב יוסף דאמרי תרוייהו: גברא אשלימת לי, גברא אשלימי לך.

Talmud: The Mishnah teaches: One who lends money to another with a guarantor cannot collect the debt from the guarantor. The Talmud at first understands that the Mishnah is ruling that a guarantor’s commitment is limited to when the debtor dies or flees. What is the reason the guarantor’s commitment is limited? Rabba and Rav Yosef both say that the guarantor can tell the creditor: You gave a man over to me, to take responsibility for him if he dies or flees; I have given a man back to you. The debtor is here before you; take your money from him, and if he has nothing, suffer the loss yourself.