Deuteronomy 20
19 Ref When you shall besiege a city a long time, in making war against it to take it, you shall not destroy the trees of it by wielding an axe against them; for you may eat of them, and you shall not cut them down; for is the tree of the field man, that it should be besieged of you?
20 Ref Only the trees of which you know that they are not trees for food, you shall destroy and cut them down; and you shall build bulwarks against the city that makes war with you, until it fall.