Deuteronomy 20:19-20

19When thou shalt besiege a city many days, in making war against it to take it, thou shalt not destroy the trees thereof by lifting up an axe against them; for thou canst eat of them; and thou shalt not cut them down, for is the tree of the field a man that it should be besieged? 20Only the trees which thou knowest are not trees for meat, thou mayest destroy and cut them down, and build bulwarks against the city that maketh war with thee, until it fall.