Albert Barnes Commentary Job 15:5

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

For your mouth utters your iniquity - Margin, “teaches.” That is, “your whole argument shows that you are a guilty man. A man who can defend such positions about God cannot be a pious man, or have any proper veneration for the Most High.”

A man may pursue an argument, and defend positions that will as certainly show he is destitute of religion as if he lived an abandoned life. Moreover, he who holds opinions that are dishonorable to God can no more be a pious man than if he dishonored God by violating His law.

You choose the tongue of the crafty - Instead of pursuing an argument with candor and sincerity, you have resorted to miserable sophisms, such as glib debaters use. You have not shown a disposition to ascertain and defend the truth, but have relied on the arts and evasions of the subtle disputant and the rhetorician. His whole discourse, according to Eliphaz, was a work of mere art, designed to blind his hearers; to deceive them with a favorable opinion of his piety; and to give some plausible, but delusive view of the government of God.