Comentario sobre Génesis 8:19

למשפחתיהם AFTER THEIR FAMILIES — They took upon themselves to keep to their specie.

כל החיה, as we explained on verse 17. הרמש וכל העוף, followed by כל הרומש על הארץ, including both the domesticated animals and the free-roaming beasts.

למשפחותיהם יצאו מן התבה, “they left the ark according to their respective families.” In Sanhedin 108 this is understood as למשפחותיהם ולא הם.This statement is not elaborated on there. [The simplest interpretation is that only those animals capable of reproducing left the ark; any animal which was sterile did not live on after the deluge for any length of time. Some commentators believe that whereas the animals left the ark without awaiting instructions from either Noach or G’d, Noach and family awaited such instructions. Noach demanded a promise from G’d that He would not again bring a flood upon the earth. Still other commentators view the word למשפחותיהם here as a hint that the animals undertook henceforth to mate only with their own species.