Keilim, Chapter 14, Mishnah 5. The Mishnah before this one listed the metal fittings of an ox drawn wagon that are considered genuine keilim and can therefore become tamei. Our Mishnah turns the list over and presents the opposite side: the metal pieces attached to that same wagon which never become tamei at all. It then moves on to two further subjects, the metal footwear placed on animals, and the moment at which a rusted blade regains the status of a utensil.
The Mishnah opens: "Hatehorin sheba'agalah", these are the parts of the wagon that remain tahor.
A Wooden Yoke With Metal Over It
"Ha'ol hamesupeh", a yoke made of wood whose surface is plated with metal. A yoke fashioned out of metal itself is a kli and is susceptible to tum'ah. But when the yoke is essentially a wooden beam and the metal is only a covering laid over it, the metal is subordinate to the wood, and such a yoke cannot become tamei.
Decorative Wings, Chimes and Bells
"Uchenafayim ha'asuyot lenoy", the projecting tips at the ends of the crossbar when they were formed purely for appearance. Had they served to fasten the animal into the yoke they would be functional metal parts, but here they contribute nothing to the harnessing and exist only as ornament.
"Ushefoferot hamashmi'ot et hakol", the little tubes that produce sound. As the animal walks these pieces knock against one another and give off a faint, pleasant ringing. They accomplish nothing practical for the wagon or for the driver; they simply make the journey nicer to listen to.
"Veha'avar shebetzad tzavarei behemah", the bells strung on either side of the throat of each animal in the team. Their purpose, like that of the pieces just listed, is nothing more than adornment.
The Wheel Rim, the Hanging Sheets and the Plating
"Hasovev shel galgal", the wheel's encircling band: the metal hoop fitted around the wooden wheel to guard it against the stones of the roadway.
"Hatasim", the metal sheets that hang down from the yoke as decoration.
"Vehasipuyim", the plating, that is, the metal sheeting that overlays the wooden portions of the wagon for the sake of appearance.
"Ushe'ar kol hamasmerot", together with every other nail found on the wagon, meaning those hammered in for decorative effect and not those that hold the wagon's components together. Of every item enumerated in this list the Mishnah rules: "tehorin", none of them is capable of contracting tum'ah.
The Two Reasons Behind the List
Two distinct principles are operating here. The plated wooden yoke and the band around the wheel are cases of metal that is secondary to the wood it covers; the wood is the essence of the item, and the metal has no independent standing as a kli. All the other cases are different: those pieces exist only for beauty, for adornment, or for producing an agreeable sound. They are not there to perform a service for a human being, and an object that renders no service does not attain the status of a kli that can receive tum'ah.
Metal Footwear for Animals
The Mishnah now takes up the coverings strapped onto animals to keep their hooves from being damaged. Its wording is "Sandalei behemah shel matachot", animal sandals fashioned from metal, and of these it rules "teme'in", they are susceptible to tum'ah; but "shel sha'am, tehorin", ones woven out of reed cannot become tamei.
This requires explanation, since as a rule an implement whose purpose is to serve an animal rather than a person is not susceptible to tum'ah. The metal shoe, however, had a second use: soldiers on the battlefield would fill such a shoe with water and drink out of it. Because it serves a person in that way, it counts as a kli and can become tamei. A shoe woven of reeds, by contrast, would never have been used by soldiers for drinking, so it has no human function at all and stays tahor.
When Does a Repaired Blade Become a Kli Again?
The closing clause of the Mishnah turns to cutting implements. When rust has eaten into a blade to the extent that it can no longer perform its work, the item has forfeited its standing as a kli and tum'ah no longer applies to it. Should someone later restore it, that standing comes back. What the Mishnah now supplies is the exact point in the restoration process where the change takes effect, which amounts to identifying when the blade is once again fit for use.
"Hasa'if me'eimatai mekabel tum'ah?", at what stage does a rusted sword re-enter the category of things that receive tum'ah, in other words, when has it become a utensil again? The Mishnah answers "misheyashupenu", as soon as it has been rubbed down with a file. When the smith has worked the surface and returned the sword to a finished condition, it can serve its purpose, and tum'ah applies to it from then on.
"Vehasakin misheyashchizenah", a rusted knife, however, becomes susceptible only once it has actually been sharpened. Filing the surface smooth is not sufficient in its case, because a knife cannot do its job at all unless the blade itself has an edge.
Taken together, the Mishnah teaches us a single consistent measure. A piece of metal counts as a kli when it genuinely serves a person: not when it merely decorates, not when it merely pleases the ear, not when it merely covers wood that is doing the real work, and not while it lies rusted and unusable. The moment it becomes capable of its own service, whether by being filed smooth or by being given a sharpened edge, it enters the world of tum'ah and taharah.