Comentario citado sobre Génesis 7:15

שנים שנים באו אל נח. They came to Noach in pairs. The Torah points out that these animals came of their own volition; Noach did not have to search for them or catch them. One of the reasons the Torah does not mention seven pairs of pure animals here is that only the number of animals that came to the ark to maintain their species are mentioned here. G'd guided them to the ark and Noach admitted them. The additional animals that served as תשלום, payment, Noach had to provide himself. You find this confirmed in verse 15 when the animals that came to the ark are specifically described as being only pairs.

FOR ALL FLESH HAD CORRUPTED THEIR WAY. If we were to explain all flesh in its usual sense and thus say that even cattle, beasts and fowl corrupted their way by consorting with other species, as Rashi has explained, we must then say that the expression, for the earth is filled with violence through them,²⁵Verse 13. does not mean “because of all of them” but only because of some of them [since “violence” does not apply to beasts and cattle], and Scripture tells of the punishment of man alone [even though all flesh corrupted their way]. Or we may say that the cattle, beasts, and fowl also did not follow their natural instincts, and all cattle seized prey and all fowl became birds of prey; thus they too committed violence.
By way of the simple meaning of Scripture, all flesh means “all men.” Further on Scripture says explicitly: all flesh wherein is the breath of life;²⁶Genesis 7:15. and of every living thing of all flesh,²⁷Ibid., 6:19. meaning all living bodies. But here it says all flesh, meaning all people. Similarly [we find the verses]: All flesh shall come to worship before Me,²⁸Isaiah 66:23. [meaning “all people”]; Or when the flesh hath in the skin thereof,²⁹Leviticus 13:24. [where again reference is only to people].