And sowed it with salt In token of his desire of their utter and irrecoverable destruction. For places situated in a salt soil being barren by nature, the sowing of salt upon a place was a symbolical custom among the eastern people, at that time, to express great hatred and anger against any place, being as much as to express a desire that it should never be inhabited again, or produce its usual products, but become barren like a salt soil. For we cannot imagine that sowing of salt could render any soil barren ever after, but rather in some time more fruitful.
Related Commentaries of Judges 9:45
Judges 9:45
45 And Abimelech fought against the city all that day; and he took the city, and slew the people that was therein, and beat down the city, and sowed it with salt.