Albert Barnes Commentary Psalms 10:7

"His mouth is full of cursing and deceit and oppression: Under his tongue is mischief and iniquity." — Psalms 10:7 (ASV)

His mouth is full of cursing - Profanity; blasphemy against God. In the previous verse, the writer had described the feelings of the heart; he now proceeds to specify the open acts of the wicked. The meaning is that the wicked man, as described here, was one who was full of imprecation, swearing, and execration; a profane man; a man who, whatever his belief about God, would constantly call upon his name and imprecate his wrath on himself or others.

An atheist, strange as it may seem, is as likely to make frequent use of the name of God, and to call upon Him, as other people; just as profane people, who have no belief in the Saviour, swear by Jesus Christ. This passage seems to be referred to by the apostle Paul in (Romans 3:14), not as a direct quotation, as if the psalmist referred to the point which he was arguing, but as language that expressed the idea that the apostle wished to convey. See the note at that passage.

And deceit - Margin, as in Hebrew, “deceits.” The meaning is that he was false and treacherous, and perhaps also that his treachery and fraud were accompanied by the solemn sanction of an oath or an appeal to God, as is likely to be the case among fraudulent and dishonest people.

And fraud - The word used here—תך tôk—is now commonly supposed to mean rather “oppression or violence.” See Gesenius’ Lexicon. When this is attributed to his mouth, it means that what he says—what he requires, what he commands—is unjust, unreasonable, and oppressive.

Under his tongue - Perhaps alluding to the serpent, whose poison is concealed at the root of the fang or tooth, and therefore under the tongue. The meaning is that beneath what the wicked say, though it seems to be harmless, as the tongue of the serpent does, yet there lies mischief and iniquity, as the poison is hidden beneath the serpent’s tongue.

Is mischief - The word used here properly means labor, toil; then trouble, vexation, sorrow. The meaning here seems to be that there lies under the tongue that which gives or causes distress; namely, wrongdoing; injustice to others.

And vanity - Margin, iniquity. This expresses the idea in the original word. Whatever he says is evil and is fitted to produce trouble and sorrow, as the concealed poison in the mouth of the serpent causes pain and death.