Rashi on Genesis 10:11/רש"י על בראשית י׳:י״א

1‘מן הארץ וגו OUT OF THAT LAND WENT FORTH ASSHUR — As soon as Asshur saw that his sons listened to Nimrod, rebelling against the Omnipresent by building the Tower, he went forth out of their midst (Genesis Rabbah 37:4).