Kommentar zu Wajikra 11:12

'כל אשר אין לו וגו‎ WHATEVER HATH NO [FINS] etc. — For what purpose is this repeated? Because I might think that in verse 9 I have only the law that permits the eating of a fish which brings up its signs of cleanness (i. e. fins and scales) to dry land. Whence, however, could I learn that if it sheds them whilst it is in the waters such is also permitted as food? Therefore it states here: whatever hath no fins and scales in the water [that shall be an abomination to you]”. Thus, if it did have them whilst it was in the water, even though it shed them when it came up on dry land, it is permissible as food! (Sifra, Shemini, Section 3 11).

What does this verse tell [us]? This is an extra verse, for it is written above (v. 10): “All that do not have fins...”

שקץ הוא לכם, “it is detestable for you.” When this expression is used it means we must not even trade in such animals, much less not eat them. (Sifra)

I might know only... I.e., were this verse not written, I would have thought: “I know only...”

כל אשר אין לו סנפיר וקשקשת, any (marine) creature without fins or scales, etc.;” the reason why the Torah does not mention any of these species by name is that the vast majority of them is hidden from our view by being under water.

Although it lost them in being brought up. However, this cannot be derived from the first verse (10), for if so, it should say “in the water,” and not “in the oceans and rivers.” Rather, it teaches that in the oceans and rivers, which are running, flowing water, the fish without signs are forbidden, but in vessels, ditches, and cisterns, even though they have no signs they may be eaten. See there (Chulin 67a).