what I want to say is no big deal, however it seems to me to mention it is worth something. The Rambam (Maimonides) decided the law (in laws of loans 13 law 4) that if a borrower admits the guarantee is worth less than the loan, that he pays the remainder [because he admits at least to that much] and takes an oath on the value of the pledge and pays nothing more [if the pledge was lost by negligence. The Ramban (Nachmanides) however asks on this is this not a case of 50 I admit I owe, and the other 50 I do not know, in which case the remainder is not paid. Rav Shach brings an answer to this question from Bava Metzia page 100 where Sumchos admits the law of dividing in a case of an oath from the Torah. Rav Shach learns from that that when the Torah requires one side to take an oath, the other side cannot claim they do not believe the oath]. My question here is that I vaguely recall some discussion in the Avi Ezri about this issue. First of all, the oath that the lender takes that the pledge is not is his domain is not mentioned in the Torah at all. It is mentioned by Rav Huna, and the Rambam does decide that it is required, but it might be only an oath from the words of the sages.---------------------------------------what I want to say is no big deal, however it seems to me to mention it is worth something. The רמב''ם decided the law (in ה' מלווה ולווה י''ג הלכה ד') that if a borrower admits the guarantee is worth less than the loan, that he pays the remainder [because he admits at least to that much] and takes an oath on the value of the pledge and pays nothing more [if the משכון was lost by negligence. The רמב''ן however asks on this, "Is this not a case of חמישים I admit I owe, and the other חמישים I do not know," in which case the remainder is not paid. רב שך brings an answer to this question from בבא מציעא דף ק' where סומכוס admits the law of dividing in a case of an oath from the תורה. ANDרב שך learns from that that when the תורה requires one side to take an oath שהוא דאורייתא , the other side cannot claim they do not believe the oath]. My question here is that I vaguely recall some discussion in the אבי עזרי about this issue. First of all, the oath that the lender takes that the pledge is not is his domain is not mentioned in the תורה at all. It is mentioned by רב הונא, and the רמב''ם does decide that it is required, but it might be only an oath דרבנן.--- In the meantime i will try to recall where i saw this question about the oath, "It is not in my domain."