Deuteronomy 20:18-19

18Otherwise, they will teach you to do all the disgusting things they do for their gods, and you will sin against the Lord your God.

19This is what you must do whenever you blockade a city for a long time in order to capture it in war. Don’t harm any of its fruit trees with an ax. You can eat the fruit. Never cut those trees down, because the trees of the field are not people you have come to blockade.