Deuteronomy 20:19
When thou shalt besiege a city a long time, in making war against it to take it, thou shalt not destroy the trees thereof by forcing an axe against them: for thou mayest eat of them, and thou shalt not cut them down (for the tree of the field is man’s life) to employ them in the siege:
The instruction belongs to the body of laws rehearsed for Israel just before crossing the Jordan into the promised land, to recall what God had taught them and their duty to keep His law. In a prolonged siege undertaken to capture a city, it forbids destroying the trees by forcing an axe against them, because their fruit may be eaten for food. Trees and vegetation are necessities of human life, and for that reason they must not be destroyed even in war. The declaration that the tree of the field is man's life means that the tree sustains human life by providing food for him.
The declaration illustrates naming a thing for what it causes or provides. As the tree is called life because it sustains life, so the law is called death because through sin it becomes the cause of death to sinners. By the same principle of naming a means by the result it brings about, as the tree is called a person's life because it sustains him, so the law can be called life because keeping it leads to life, and death because it condemns the sinner and brings death.
The same principle of preserving the necessities of life in war applies to Revelation 7:1, where God restrains the devastation of universal war so that the necessities of life are preserved until His work is done. The prohibition on harming vegetation resembles the command Abubeker gave his forces to spare fruit trees and fields, which may have suggested his decree.