Gittin 12A

דלמא לא היא; עד כאן לא קאמר רבי אליעזר התם, אלא דמיגו דאי בעי מפקר להו לנכסיה, והוי עני וחזי ליה ⁠– ומיגו דזכי ליה לנפשיה זכי לחבריה; אבל הכא, לא.

Perhaps that is not so. Perhaps this is not the point of dispute between R' Eliezer and the Rabbis. There are two ways to explain why this might not be the case. First, it is possible that R' Eliezer states his opinion only there, when the person took possession of the pe’a despite not being eligible to collect it for himself, since if the one who collected the produce desired, he could declare his property ownerless and become a poor person, and then the produce would have been fit for him to retain for himself. And since he could have acquired the pe’a for himself, he can likewise acquire it for another as well. However, here, where he seizes property on behalf of a creditor, he cannot seize this property for himself. Consequently, R' Eliezer does not rule that he can do so when it is against the interests of another person.

ועד כאן לא קאמרי רבנן התם, אלא דכתיב: ״לא תלקט לעני״⁠ – לא תלקט לו לעני; אבל הכא, לא.

Second, one can argue from the opposite perspective: The Rabbis state their opinion only there, that one cannot acquire on behalf of the poor person, as it is written: “The corner of your field you should not reap and the gleaning of your harvest you should not gather; for the poor you should leave them” (Leviticus 23:22), and the rabbis expounded this verse by reading it as though there were no break in the middle: You should not gather for the poor, i.e., the poor person must collect the produce for himself. However, here, where one seizes property on behalf of a creditor, this verse does not apply, and therefore the Rabbis did not rule that the action of the third party is ineffective. Consequently, it is possible that the dispute between R' Eliezer and the Rabbis is not with regard to the issue of whether one can seize property on behalf of a creditor in a case where it is to the detriment of others.