Gittin 4a: Eidei Chasima vs. Eidei Mesira in Get and Kiddushin

The shiur analyzes a fundamental dispute between Tosfos and the Rambam (רמב"ם) regarding when eidei chasima (witnesses who sign the get) can serve in place of eidei mesira (witnesses to the actual delivery). Tosfos on Gittin 4a proves from multiple sources that we hold like Shmuel that by sh'tar sh'taros (standard documents), the halacha (הלכה) is eidei mesira karsei—the witnesses to the delivery establish the document's validity. Since this is the din by regular documents, the same must apply to gittin. Therefore, Tosfos argues, when Rav Elazar says eidei chasima suffice if the eidei mesira are unavailable, this only works because we assume there probably were kosher witnesses at the delivery. But if we know for certain there were no eidei mesira, the get is invalid. The shiur explores why Tosfos' position creates a logical difficulty. A get serves two functions: it is both a shtar (a document effectuating a kinyan/acquisition) and a sefer kreisos (a religious instrument of severance). If the halacha by sh'tar sh'taros were that eidei chasima karsei, then the shtar aspect of the get would be established through the witnesses who sign it. The sefer kreisos aspect would still require eidei mesira, but if those witnesses died, perhaps the eidei chasima could testify about the mesira as well. However, since Tosfos holds that by sh'tar sh'taros the din is eidei mesira karsei, the eidei chasima accomplish nothing—they are essentially meaningless. Therefore, one cannot rely on them for the mesira unless we assume there actually were kosher eidei mesira present.