John Gill Commentary Job 8:12

"Whilst it is yet in its greenness, [and] not cut down, It withereth before any [other] herb." — Job 8:12 (ASV)

Whilst it [is] yet in its greenness Before it is come to its full height, or to a proper ripeness; when it has not yet flowered, or is about it; before the time usual for it to turn and change; it being without moisture, water, or watery clay, will change;

[and] not cut down by the scythe, or cropped by the hand of man,

it withereth before any [other] herb of itself; rather sooner than those that do not require so much moisture; or in the sight and presence of them, they looking on, as it were, and deriding it; a poetical representation, as Schultens observes: next follows the accommodation of these similes to wicked and hypocritical men.