ויקרא, פרק ט״ו, פסוק י״ז

The laws of ritual impurity extend beyond human beings, affecting inanimate objects that come into contact with bodily secretions. When a seminal emission occurs, the requirement for purification spreads to the physical items involved. Any cloth or leather item that comes into contact with semen becomes ritually impure and must undergo a washing process. However, the primary approach among commentators is that this rule is not limited strictly to fabric and leather. Rather, it applies to all vessels and objects capable of contracting impurity [רלב״ג, ביאור יש״ר, רד צ הופמן]. The specific mention of clothing and leather products is simply a matter of practical reality. Because these materials are soft and typically used for bedding, they are the items most likely to be exposed to such emissions [רלב״ג]. Furthermore, an item does not need to be completely covered to become impure; contact with even a small portion of the object is sufficient to require purification [אדרת אליהו].

A central condition for this impurity involves the physical state of the fluid itself. By comparing various laws, commentators determine that semen only transfers impurity when it remains in its natural, original state, meaning it still retains the potential to fertilize [תורה תמימה]. Consequently, if the fluid has spoiled or degraded, it completely loses its capacity to make an object impure [חזקוני, אדרת אליהו]. This specific distinction is rooted in oral tradition, which defines the exact boundaries of impurity. Without this received tradition, basic logic might assume that the affected item requires washing in every circumstance, regardless of whether the substance on it is wet or already dried out [אבן עזרא].