Ibn Ezra on Genesis 7:7/אבן עזרא על בראשית ז׳:ז׳

1BECAUSE OF THE WATERS OF THE FLOOD. Because of fear of the waters of the flood. In these seven days many of the clean animals and fowl came of their own volition to the vicinity of the ark. From the others and from everything that creeps, a pair consisting of a male and female of each kind came to the ark.