ויקרא, פרק י״ד, פסוק מ״ו

The laws of an afflicted house establish different degrees of impurity based on the structure's physical state and the nature of a person's visit. To be considered as having entered the house, an individual must bring their head and the majority of their body inside [תורה תמימה, אדרת אליהו, רש״ר הירש]; inserting a single limb is not sufficient [מלבי״ם]. Furthermore, entering the structure backwards does not constitute a forbidden entry [תורה תמימה]. However, once a person properly enters, even for a fleeting moment without lingering, they immediately become impure [רבנו בחיי, ביאור יש״ר, בכור שור, רש״ר הירש, הופמן].

The timeframe for this impurity applies during the first and second weeks of the house's quarantine [ביאור יש״ר, הופמן, חומש קה״ת]. Yet, a crucial legal distinction exists regarding the days when the house is being actively treated. During the period when infected stones are removed and the walls are scraped, just before a new quarantine week begins, the house does not transmit impurity to those who enter [רש״י, מזרחי, שפתי חכמים, מלבי״ם, משכיל לדוד, אדרת אליהו, חזקוני, דברי דוד]. In contrast, if the affliction returns and the house is condemned to be demolished, the impurity is absolute. In such a house, even if the affected areas are scraped and the stones removed, the impurity remains fully intact, and anyone entering is affected [רש״י, מזרחי, תורה תמימה, שפתי חכמים, מלבי״ם, בכור שור, חזקוני, אדרת אליהו, דברי דוד, הדר זקנים].

When a person becomes impure from entering the house, the impurity lasts until evening, and they must wash their body in water to become pure [אבן עזרא, חזקוני]. The primary approach among commentators notes that a brief entry only affects the person's body, leaving their clothing pure. This exemption for clothing, however, applies strictly to a short visit. Actions such as eating or lying down inside the house serve as practical examples of a prolonged stay. If a person remains inside for a defined period, the severity of the impurity increases, causing their clothes to become impure and require washing as well [רש״י, מזרחי, רבנו בחיי, שפתי חכמים, מלבי״ם, משכיל לדוד, לבוש האורה, אדרת אליהו, גור אריה, רש״ר הירש, דברי דוד].

The exact duration that triggers this more severe impurity is measured by the time it takes to eat half a loaf of bread, which is equivalent to the volume of four eggs. To precisely define a significant, established meal, this measurement is based on the time it takes to eat wheat bread, which is consumed more quickly than barley bread, while the person is reclining and eating with a dip or relish [מזרחי, שפתי חכמים, מלבי״ם, משכיל לדוד, גור אריה, רש״ר הירש, דברי דוד].