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 Mishnah (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 (= page) 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 Mishnah, 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 baraitacontrasts a case where the claim is made that a large menorah was given for safekeeping and the defendant admits to having received a small menorah vs. a case where the claim is made that a menorah weighing ten litrim was given and the defendant admits to a menorah 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 Yitzhak suggests that we are dealing with a case of a menorah shel huliyot – a menorah made of pieces – and that the plaintiff admitted to having received a smaller number of pieces than was claimed.