Charles Ellicott Commentary Job 15:5

"For thine iniquity teacheth thy mouth, And thou choosest the tongue of the crafty." — Job 15:5 (ASV)

Your mouth utters your iniquity. — These words may mean either that “Your mouth teaches your iniquity,” or that “Your iniquity teaches your mouth.” If the former, the second clause of the verse is taken adversatively, meaning: “Your mouth proclaims your iniquity, though you choose the tongue of the crafty, and so you contrive in some degree to conceal it.” If the latter, the second clause is understood as a consequence: “Your iniquity teaches your mouth its eloquence, and as a consequence, you choose the tongue of the crafty.” We incline to the latter, though it is fair to say that the next verse seems rather to favor the other meaning.