Isaiah 9:18

Three things are here promised, and they all point ultimately at the grace of the gospel, which the saints then were to comfort themselves with the hopes of in every cloudy and dark day, as we now are to comfort ourselves in time of trouble with the hopes of Christ's second coming, though that be now, as his first coming then was, a thing at a great distance.

For wickedness - Wickedness rageth like a fire, destroying and laying waste the nation: but it shall be its own destruction, by bringing down the fire of God’s wrath, which shall burn up the briers and the thorns; that is, the wicked themselves. Briers and thorns are an image frequently applied in Scripture, when set on fire, to the rage of the wicked; violent, yet impotent, and of no long continuance. “They are extinct as the fire of thorns,” Psa 118:

"They (the thickets of the forest) shall lift themselves proudly aloft [the Hebrew is from a Syriac root, a cock, expressing stateliness of motion, from his strutting gait, HORSLEY], in (in passing into) volumes of ascending smoke" [MAURER].

For wickedness - This commences the third part of the prophecy, which continues to the end of the chapter. It is a description of prevailing impiety. The effects and prevalence of it are described by the image of a raging, burning flame, that spreads everywhere: first among the humble shrubbery - the briers and thorns, then in the vast forests, until it spreads over the land, and sends a mighty column of flame and smoke up to heaven. Burneth as the fire - Spreads, rages. extends as fire does in thorns and in forests. In what respects it burns like the fire, the prophet immediately specifies. It spreads rapidly everywhere, and involves all in the effects. Wickedness is not unfrequently in the Scriptures compared to a fire that is shut up long, and then bursts forth with raging violence. Thus Hos 7:6: Truly, in the inmost part of it, their heart is like an oven, While they lie in wait; All the night their baker sleepeth; In the morning it burneth like a blazing star. ‘As an oven conceals the lighted fire all night, while the baker takes his rest, and in the morning vomits forth its blazing flame; so all manner of concupiscence is brooding mischief in their hearts, while the ruling faculties of reason and conscience are lulled asleep, and their wicked designs wait only for a fair occasion to break forth.’ - Horsely on Hosea; see also Isa 50:2; Isa 65:5. It shall devour - Hebrew, ‘It shall eat.’ The idea of devouring or eating, is one which is often given to fire in the Scriptures. The briers and thorns - By the briers and thorns are meant, doubtless, the lower part of the population; the most degraded ranks of society. The idea here seems to be, first, that of impiety spreading like fire over all classes of people; but there is also joined with it, in the mind of the prophet, the idea of punishment. […]