ויקרא, פרק ט״ו, פסוק י״ב

The severe ritual impurity of a man with a bodily discharge deeply affects the objects in his environment, creating distinct rules for different types of materials. A fundamental distinction exists between simple earthenware and more durable items like wood or metal, dictating how their impurity is contracted and resolved.

A foundational rule of ritual purity is that an earthenware vessel cannot become impure from the outside; contamination only occurs if the source of impurity enters its interior airspace. The primary approach among commentators is that this principle remains unchanged even when dealing with the unusually severe impurity of a man with a discharge [רש״י, מזרחי, תורה תמימה, חזקוני, ברטנורא].

This raises a question regarding how such a vessel becomes impure through external physical contact. If it only contracts impurity from within, standard touching from the outside should have no effect. The primary approach among commentators is that this contact does not refer to standard physical touch, but rather to the concept of shifting. If the impure individual moves or shakes the entire vessel, even indirectly using an object like a stick, the vessel becomes impure [רש״י, מזרחי, שפתי חכמים, רלב״ג, מלבי״ם, גור אריה]. This shifting is equated with direct touch to teach that the movement must be performed by exposed, external limbs, such as hands, rather than hidden parts of the body [מזרחי, שפתי חכמים, גור אריה].

Offering a physical explanation for this phenomenon, [הכתב והקבלה] suggests that inserting a hand into an earthenware vessel displaces its internal air particles. Because the vessel's purity status depends entirely on its airspace, any movement or shaking by the impure person shifts the internal air, rendering the action equivalent to touching the air itself. Conversely, [רש״ר הירש] maintains that this specific scenario of shifting is the singular exception in Jewish law where an earthenware vessel actually does contract impurity from the outside.

Once an earthenware vessel, or a vessel made of similar materials like natron, becomes impure, it must be broken [מלבי״ם, אדרת אליהו]. This does not mean there is an active command to smash the item, but rather that breaking it is the only possible method of purification, as water is entirely ineffective [ברכת אשר, שטיינזלץ].

In contrast, vessels made of wood, metal, and other higher-grade materials are treated differently [בכור שור, פרדס יוסף, שטיינזלץ]. These items can be restored to purity. They require immersion in a ritual bath, accompanied by a thorough washing and scrubbing to remove any physical dirt that may have adhered to them [ביאור יש״ר, רש״ר הירש, הופמן].

Additionally, the treatment of these purifiable items highlights the law regarding objects situated above the impure individual. Vessels, food, or drinks that are carried or placed directly over the person contract a lighter degree of impurity. Unlike items the person directly lies or sits upon, which suffer a severe contamination, objects located above him only require standard immersion in water to be purified [מלבי״ם, אדרת אליהו].