Though the root thereof wax old - Though life becomes almost extinct. The idea is, though the root of the tree be very old, yet it does not become wholly lifeless. It is not like an old man, when life goes out altogether. In the very aged root there will be vitality still; but not so in man.
Though the stock thereof - The stump - literally that which is cut off - גזעוּ geza‛ô. The meaning is, that when the trunk of the tree is cut down and dies altogether, life remains in the root; but when man fails, life is wholly extinct.