Radak, on Ps 9:7

“The swords of the enemy have failed unto the end: and their cities thou hast destroyed. Their memory hath perished with a noise.”

“His mouth is full of swearing, deceit, and fraud: – Such is the way of the wicked; when he wishes to deceive others he swears to them with a full mouth, so that he may seem to swear in all sincerity, and this is deceit and fraud. Fraud also is the same as deceit, because there is not really in his heart what he pretends with his mouth. Under his tongue is mischief and iniquity: – When he takes an oath with his tongue, under his tongue is mischief and iniquity. The heart is under the tongue, hidden from what is revealed by the tongue. So also (in the verse) “high praise was under my tongue” (Ps. 66:17); he (the Psalmist) is speaking of the heart. And מלא (full) is not an adjective, but a verb, as: “and the glory of the Lord filled (מלא) the tabernacle” (Exod. 40:34). He says: he fills his mouth with swearing so that a man may trust him, and then he plays him false.”

Imported from an open dataset — not yet checked against the printed edition.