Kommentar zu Bereschit 6:20

מהעוף למינהו OF THE FOWLS AFTER THEIR KIND— those that had kept to their own species and had not corrupted their way (taking the words to mean, “of the fowls that had kept to their own kind”). All these came of their own accord, but only those which the Ark was allowing to pass in did Noah permit to enter (Sanhedrin 108b).

TWO OF EVERY SORT SHALL COME UNTO THEE, TO KEEP THEM ALIVE. G-d thus informed Noah that two of every sort would come of their own accord, and he would not find it necessary to hunt for them in the mountains and distant lands, and he would bring them into the ark after that. At the actual narration [of their coming, Scripture] explains⁵⁹Genesis 7:16. that they came male and female; this is implied here. After that, He commanded him to take seven and seven of every clean beast.⁶⁰Ibid., 7:2. Concerning these, G-d did not say that they would come of their own accord but that Noah should take them.⁶¹The verse states: Of every clean beast thou shalt ‘take’ to thee seven and seven. Noah brought sacrifices after the flood from the clean beasts and fowl. (See Chapter 8, Verse 20.) The reason for this is that those who came to be saved and to keep their seed alive⁶²Chapter 7, Verse 3. did come of their own accord, but for those who were to be sacrificed as whole offerings, G-d did not decree that they come of their own accord to be slaughtered. Rather, Noah took them since the purpose of the command to take seven and seven was that Noah bring a sacrifice from them after the flood.
The meaning of the word “clean” is that the Holy One, blessed be He, explained to Noah the signs of ritual cleanliness for beast and fowl. Scripture, however, refers to it briefly by saying, “clean,” in accordance with the Torah.⁶³See Leviticus, Chapter 11. But Rashi wrote: “Clean, meaning that which in the future will be permitted to Israel as clean; we thus learn that Noah studied the Torah.”
From here we derive that the sacrifices of the sons of Noah⁶⁴See Seder Bereshith, Note 222. must also be only of the clean beast and the clean fowl. So also it is said of the sacrifice of Abel: of the first-born of his flock and of the fat thereof.⁶⁵Above, 4:4. However, all clean species are permissible for them to bring as sacrifices as it is written: And he took of every clean beast, and of every clean fowl, and offered burnt-offerings on the altar.⁶⁶Genesis 8:20. [Later, when the Torah was given, G-d] added a commandment to Israel that all their sacrifices be only of the beasts and of the herd,⁶⁷Leviticus 1:2. of the turtledoves and of the young pigeons.⁶⁸Ibid., Verse 14.
Of the fowl also of the heaven, seven and seven⁶⁹Genesis 7:3. — this means the clean fowl for the verse is a continuation of the verse above: [Of every ‘clean’ beast shalt thou take to thee seven and seven].⁷⁰Ibid., Verse 2.

מהעוף למינהו. From the birds according to their kind. It is peculiar that the birds are mentioned before the mammals in this list. If the list is in order of their respective importance, the mammals should have been mentioned first; if the list is in an ascending order the crawling creatures should have been mentioned first. Why does the Torah use this peculiar order? Perhaps the birds enjoy a certain distinction over the mammals because they multiply so profusely. It is interesting that only the "pure" birds multiply so profusely; the 24 categories of "impure" birds which are not fit for consumption by Jews do not multiply as profusely. We have a tradition (Chulin 63?) according to which 120 varieties of birds were found on the Temple Mount, all of which are sub-categories of the איה, the falcon. At any rate these birds are greatly outnumbered by the "pure" birds. The Torah lists only ten categories of mammals which may be consumed by Jews. Presumably this is the reason the Torah commanded Noach to have the birds enter the ark ahead of the mammals. The difference in the description of the birds as למינהו, and the mammals as למינה, indicates that there were more categories and sub-categories of birds (compare Rashi). The Torah lists the respective categories of creatures, i.e. birds, mammals, and crawling creatures according to their relative mobility.