עירוב פרשיות כתוב כאן וכי כתיב כי הוא זה אמלוה הוא דכתיב ומאי שנא מלוה

A merging of Torah portions is written here, and the halakha written in this passage is in fact meant to be applied to a different passage. And when it is written: “ This is it, ” from which the halakha of a partial admission is derived, it is written concerning a loan, not a deposit. The Gemara asks: And what is different about a loan that this halakha would apply only there?

כדרבה דאמר רבה מפני מה אמרה תורה מודה במקצת הטענה ישבע חזקה אין אדם מעיז פניו בפני בעל חובו והאי בכולי בעי דנכפריה והאי דלא כפריה משום דאין אדם מעיז פניו

The Gemara answers: It is in accordance with the statement of Rabba, as Rabba says: For what reason did the Torah say that one who admits to a part of the claim must take an oath? It is because there is a presumption that a person does not exhibit insolence by lying in the presence of his creditor, who had done him a favor by lending money to him. And this person who denies part of the claim actually wants to deny all of the debt, so as to be exempt, and this fact that he does not deny all of it is because a person does not exhibit insolence.

ובכולי בעי דלודי ליה והאי דכפר ליה במקצת סבר אי מודינא ליה בכוליה תבע לי בכוליה אישתמיט לי מיהא השתא אדהוו לי זוזי ופרענא הלכך רמא רחמנא שבועה עילויה כי היכי דלודי ליה בכוליה

Rabba continues: And in order not to exhibit insolence, he wants to admit to the creditor with regard to all of the debt, and this fact that he denies owing him in part is because he reasons: If I admit to him with regard to all of the debt, he will lodge a claim against me with regard to all of it, and right now I do not have the money to pay. I will evade him at least for now until I have money, and then I will pay him all of it. This rationalization enables one to falsely deny part of a claim. Therefore, the Merciful One imposes an oath on him, in order to ensure that he will admit to him with regard to all of the debt.

וגבי מלוה הוא דאיכא למימר הכי אבל גבי פקדון מעיז ומעיז

The Gemara completes its answer: And it is with regard to a loan that this can be said, as the basis for this explanation is that one will not exhibit insolence before his creditor, who did him a favor by lending him money; but with regard to a deposit, one will certainly exhibit insolence, as the claimant did him no favor. Therefore, there is no reason to say that one who completely denies a claim concerning a deposit is deemed credible any more than one who admitted to part of it, and he is obligated to take an oath in either case.

תני רמי בר חמא ארבעה שומרין

§ Rami bar Ḥama teaches this baraita: All four types of bailees