C. F. Keil and Franz Delitzsch on Isaiah 10:18-19

Isa 10:18-19 “And the glory of his forest and his garden-ground will He destroy, even to soul and flesh, so that it is as when a sick man dieth. And the remnant of the trees of his forest can be numbered, and a boy could write them.” The army of Asshur, composed as it was of many and various nations, was a forest (ya‛ar); and, boasting as it did of the beauty of both men and armour, a garden ground (carmel), a human forest and park. Hence the idea of “utterly” is expressed in the proverbial “even to soul and flesh,” which furnishes the occasion for a leap to the figure of the wasting away of a נסס (hap. leg. the consumptive man, from nâsas, related to nūsh, 'ânash, Syr. n‛sı̄so, n‛shisho, a sick man, based upon the radical notion of melting away, cf., mâsas, or of reeling to and fro, cf., mūt, nūt, Arab. nâsa, nâta). Only a single vital spark would still glimmer in the gigantic and splendid colossus, and with this its life would threaten to become entirely extinct. Or, what is the same thing, only a few trees of the forest, such as could be easily numbered (mispâr as in Deu 33:6, cf., Isa 21:17), would still remain, yea, so few, that a boy would be able to count and enter them. And this really came to pass. Only a small remnant of the army that marched against Jerusalem ever escaped. With this small remnant of an all-destroying power the prophet now contrasts the remnant of Israel, which is the seed of a new power that is about to arise.