We have already established that a modeh be-miktzat – a defendant who admits to part of a monetary claim made by the plaintiff – will have to pay what he admits that he owes, and in addition will have to take a Biblical oath that he does not owe the part that he denies.
According to the Mishna (42b) there are certain limitations to this rule. Specifically, it only applies to claims that are measurable by size, weight or amount. On today’s daf Rava adds that not only the claim made by plaintiff, but also the admission of the defendant must meet this requirement. Thus, the case that is taught in the Mishna, where the claimant argues that he gave the defendant a kis maleh – a wallet that was entirely full – and in response the defendant says “I do not know what was in the wallet, but I am returning it as I received it,” would not be considered to be a case of modeh be-miktzat, even if it had less than the amount that the plaintiff claims was in it.
The Gemara continues by quoting a baraita that supports Rava’s teaching. One of the examples presented by the baraita contrasts a case where the claim is made that a large menora was given for safekeeping and the defendant admits to having received a small menora vs. a case where the claim is made that a menora weighing ten litrim was given and the defendant admits to a menora of five litrim. In the first case there is no need for an oath to be taken, while the second case is considered modeh be-miktzat since the discussion was about the weight of the object.
In explaining the difference between the two cases, Rabbi Shmuel bar Rav Yitzḥak suggests that we are dealing with a case of a menora shel ḥuliyot – a menora made of pieces – and that the plaintiff admitted to having received a smaller number of pieces than was claimed.