But the sons of Belial shall be all of them as thorns - There is no word in the text for sons; it is simply Belial, the good-for-nothing man, and may here refer - first to Saul, and secondly to the enemies of our Lord.
As thorns thrust away - A metaphor taken from hedging; the workman thrusts the thorns aside either with his bill or hand, protected by his impenetrable mitten or glove, till, getting a fair blow at the roots, he cuts them all down. The man is fenced with iron, and the handle of his bill is like the staff of a spear. This is a good representation of the dubbing-bill, with which they slash the thorn hedge on each side before they level the tops by the pruning-shears. The handle is five or six feet long. This is a perfectly natural and intelligible image.

But the sons of Belial shall be all of them as thorns thrust away,.... Not like the tender grass that springs up, and flourishes after rain, and the sunshine upon that; but like thorns, useless, hurtful, and pernicious, and fit only for burning: this is true of wicked men in general, that cast off the yoke of the Lord, and become unprofitable, as Belial signifies; and of wicked governors in particular, who, instead of being helpful, are harmful to a commonwealth; and instead of being the joy and comfort of their subjects, and of giving pleasure to them, and making them cheerful and prosperous, give pain and trouble, and cause grief and sorrow; and are, if possible, to be thrust away, and deposed from government:

because they cannot be taken with hands; thorns cannot be handled and gently dealt with, but some instrument must be used to put them away with force; so wicked men, and especially wicked rulers, are untractable, and not to be managed in a gentle way, and therefore violent ones must be taken.