ויקרא, פרק י״א, פסוק י״ב

The underwater world remains largely hidden from human sight, teeming with creatures that often go unseen. Unlike land animals and birds, which are individually listed by name when distinguishing between what is permitted and what is forbidden, aquatic creatures are not given specific names [חזקוני, פענח רזא]. Instead, general physical signs are provided to identify permitted aquatic life, with the understanding that creatures lacking these features, which make up the vast majority of water dwellers, are forbidden to eat [ביאור שטיינזלץ].

The necessary identifying marks are fins and scales. Fins are the limbs used for swimming, while scales are round, fingernail-like coverings. To be considered proper scales, they must be removable, capable of being peeled or scraped from the skin by hand or with a knife, much like tree bark. A hard shell permanently attached to the skin does not qualify [מיני תרגומא].

These specific physical traits are required because they point to a healthy nature and a refined physical makeup that is well-suited for human consumption. Scales indicate a natural body heat that purifies the creature's physical matter, while fins enable swift, easy movement that helps expel waste from the body. In contrast, water creatures with hard, immovable shells possess a coarse and unrefined physical makeup [רלב״ג].

While the instruction regarding these signs might appear repetitive, the primary approach among commentators is that this repetition introduces a crucial practical rule. The strict requirement for a fish to possess these signs applies specifically while it is in the water. Therefore, if a fish has scales while swimming but sheds them the moment it is pulled onto dry land, it remains completely permitted for consumption.

The emphatic reminder that these forbidden creatures are an abomination serves an additional purpose. It teaches that the restriction goes beyond consumption to prohibit commerce as well. A person is not allowed to trade or financially profit from forbidden fish [מלבי״ם, חזקוני, תורה תמימה]. Yet, despite this strict distancing, they are classified merely as an abomination rather than strictly impure. This distinction means that, unlike the carcass of a land animal, the dead bodies of forbidden fish do not transfer ritual impurity to a person who touches them [רלב״ג].