To understand what our sages said, “whatsoever hath scales is known to have fins. And whatsoever hath fins, it is not known if it has scales.”
In the work, we should interpret the matter of Kaskeset (scales) as Kushiot (questions) that he has in the work of God. The Kushiot are vessels in which to receive answers, since the answers are not filled in the external mind, but specifically in the internal mind, which is the Upper Light, clothed within a person. And then the questions are settled in him.
Hence, to the extent that questions increase, to that extent does the Upper Light dress within man. This is why the scales are among the signs of purity, since through it one can come to purify oneself, by not wanting to have questions. Hence, one does whatsoever one can to purify oneself, so he can be awarded the Upper Light.
And a fin, too, is among the signs of purity. Snapir (fin) implies Soneh-Peh-Ohr Elyon (hating-mouth-Upper Light). And since he has questions, it is certainly because he has hatred towards the Upper Light. But one who has fins does not have to have questions. One may hate the Upper Light not because one has questions, but because one is simply greedy, and says, “I will not go in any case.”
This is the sign of purify. That is, when he has a fish. A fish implies meat that is clothed in fins and scales. This means that the Upper Light shines in these two signs.
But one who works without any questions in the work, this is not a sign of purity, that one has no questions. This is so because one has no place in which to place the Upper Light, as one has no reason that will compel one to draw the Upper Light, as even without the Upper Light one thinks that one is just fine.
This is why when Pharaoh, King of Egypt, wanted to keep the people of Israel in his domain, he issued an order to not give Kash (straw), as it is written, “So the people were scattered… to gather stubble for straw.” Then they would never need the Creator to deliver them from the domain of the impurity into the Kedusha (Sanctity).