@Green Witch,
Just to be a bit more specific. To me, it seems a basic comedy act or bit where a character, not necessarily a mohel, picks on someone, for a small thing, like putting a glass on a table, and exagurates, or embellishes to a incredible degree, all the bad things that could happen, when the glass falls on the rug. This can be duplicated for endless situations. I suspect it to be an old comedy act. I suspect it is not original to Seinfeld at all. just a clever reconstruction of tried and true comedy sketch, probably from Vaudeville, or the Catskills or somewhere. However, I can't prove it.