Shabbos 16a

שבת ט״ז ע״א

Shabbat 16a

Learn Shabbos 16a step by step: Aramaic beside English, every question, answer and proof colour-coded.

Open Shabbos 16a in Gemara Clarity

Topic

Why כלי זכוכית (glass vessels) are compared to כלי מתכות (metal vessels) for טומאה, and where that comparison stops

Overview

The גמרא has compared glass to כלי חרס because both are made from sand. So it asks why glass is not like כלי חרס in never becoming טמא from its outer side. A משנה lists only כלי חרס and כלי נתר as sharing those rules, so glass is different. The answer: broken glass can be melted and remade, like metal, so חכמים compared it to כלי מתכות. The גמרא then asks why remade glass does not regain its old impurity (טומאה ישנה) the way metal does. It answers that glass impurity and טומאה ישנה are both only דרבנן, and חכמים do not put one rabbinic rule on top of another. Finally it asks why flat glass vessels are pure when flat metal vessels are טמא from the תורה. The answer is that חכמים made a deliberate difference (a הכירא) so people would know glass impurity is only rabbinic and would not burn תרומה or קדשים because of it.

Opening lines

The steps (9)

1. ChallengeIf glass is like earthenware, it should not become impure from outside
2. ProofA משנה shows only natron and earthenware share the same impurity rules
3. ResolutionGlass is likened to metal because broken glass can be remade
4. ChallengeThen remade glass should regain its old impurity like metal
5. ProofThe משנה on metal vessels returning to old impurity
6. ChallengeThe משנה shows remade glass is impure only from now on
7. Resolutionחכמים do not add a rabbinic impurity on top of a rabbinic impurity
8. ChallengeFlat glass vessels should at least be impure like flat metal
9. ResolutionA deliberate sign so people do not burn תרומה and קדשים