Answer: Strong men who are fully armed and ready for intense battle.

“But the sons of Belial shall be all of them as thorns thrust away, because they cannot be taken with hands: But the man that shall touch them must be fenced with iron and the staff of a spear; and they shall be utterly burned with fire in the same place.” (II Samuel 23:6-7)

Of this passage, Jamieson, Fausset, and Brown’s commentary reads:

“But the sons of Belial shall be all of them as thorns—that is, the wicked enemies and persecutors of this kingdom of righteousness. They resemble those prickly, thorny plants which are twisted together, whose spires point in every direction, and which are so sharp and strong that they cannot be touched or approached without danger; but hard instruments and violent means must be taken to destroy or uproot them. So God will remove or destroy all who are opposed to this kingdom.”

Matthew Poole’s NT commentary reads:

“The staff of a spear; so the meaning is, he must fill his hand, or arm himself with some iron weapon, whereby he may cut them down; or, with the staff of a spear, or some such like thing, whereby he may thrust them away from himself, that they do him no hurt. Or thus, he will be filled, or will fill himself, i. e. his hand, wherewith he attempted to touch and take them, with thorns, as with iron and the staff of a spear; i. e. he will be as surely and sorely wounded, as if one should run the iron head and part of the wood of a spear into his hand. And they shall be utterly burned, or, therefore; because men cannot safely touch them, therefore they will burn them up.”

John Gill comments:

“But the man [that] shall touch them must be fenced with iron and the staff of a spear, &c.] To remove these thorns, or sons of Belial, out of the way, or to defend himself against them; or weapons of war must be made use of to conquer and destroy them.”