James 2:20

“But wilt thou know, O vain man, etc.] These are the words of the apostle reassuming the argument, that faith without works is dead, useless, and unprofitable; and the man that boasts of his faith, and has no works to show it, he calls a “vain man”, an empty one, sounding brass, and a tinkling cymbal; empty vessels make the greatest sound; such are proud boasters, vainly puffed up by their fleshly mind; but are empty of the true knowledge of God, and of the faith of Christ, and of the grace of the Spirit: the Syriac version renders it, “O weak”, or “feeble man”, as he must needs be, whose faith is dead, and boasts of such a lifeless thing; and the Ethiopic version renders it, “O foolish man”,…”

“wilt thou know--"Vain" men are not willing to know, since they have no wish to "do" the will of God. James beseeches such a one to lay aside his perverse unwillingness to know what is palpable to all who are willing to do. vain--who deceivest thyself with a delusive hope, resting on an unreal faith. without works--The Greek, implies separate from the works [ALFORD] which ought to flow from it if it were real. is dead--Some of the best manuscripts read, "is idle," that is, unavailing to effect what you hope, namely, to save you.”

“But wilt thou know - Will you have a full demonstration of it; will you have the clearest proof in the case. The apostle evidently felt that the instances to which he was about to refer, those of Abraham and Rahab, were decisive. O vain man - The reference by this language is to a man who held an opinion that could not be defended. The word “vain” here used (κενε kene) means properly “empty,” as opposed to “full” - as empty hands, having nothing in them; then fruitless, or without utility or success; then false, fallacious. The meaning here, properly, would be “empty,” in the sense of being void of understanding; and this would be a mild and gentle way of saying of one that he was foolish,…”

“But art than willing to know - Indeed thou art not: thou wouldest fain be ignorant of it. O empty man - Empty of all goodness. That the faith which is without works is dead - And so is not properly faith, as a dead carcase is not a man. James 2:21”

“2:20-26 James demonstrates from Scripture that genuine faith finds expression in action.”

“O vain: Jam 1:26; Job 11:11, Job 11:12; Psa 94:8-11; Pro 12:11; Jer 2:5; Rom 1:21; Co1 15:35, Co1 15:36; Gal 6:3; Col 2:8; Ti1 1:6; Tit 1:10 that: Jam 2:14 James 2:21”