Deuteronomy 20:18-20

Young's Literal Translation

¹⁸ so that they teach you not to do according to all their abominations which they have done to their gods, and ye have sinned against Jehovah your God.

¹⁹ `When thou layest siege unto a city many days, to fight against it, to capture it, thou dost not destroy its trees to force an axe against them, for of them thou dost eat, and them thou dost not cut down -- for man's [is] the tree of the field -- to go in at thy presence in the siege.

²⁰ Only, the tree, which thou knowest that it [is] not a fruit-tree, it thou dost destroy, and hast cut down, and hast built a bulwark against the city which is making with thee war till thou hast subdued it.