The expression “He says in his heart” is a biblical way of saying “he thinks, he says to himself,” which may be rendered in some languages by the same figurative expression or by a similar idiom.
I shall not be moved translates the causative of the verb meaning to totter, stagger, fall (see 13.4; 15.5; 16.8).
In line b some scholars take the Hebrew phrase “to generation and generation” to refer to the descendants of the wicked man, who believes that they will always be free from trouble. Most, however, take the expression to mean “at all times, forever,” or combined with the negative, “never.” But it should be noticed that line b, “I will never be in trouble” (Good News Translation), may be considered as part of what the psalmist is saying about the wicked man, as follows: “(the man) who is never in trouble”; so New Jerusalem Bible and Hebrew Old Testament Text Project. However, the interpretation followed by the majority seems to be preferable.
The second line of this verse is an example of shifting to a heightened expression for the purpose of emphasizing the impossibility of the wicked person being in trouble. Good News Translation do.
“Is quick to speak” (Good News Translation) translates under his tongue. Some scholars see here the idea of such words being to the liking of the evil man; they are like tasty morsels which he savors (Kirkpatrick); see Job 20.12. Traduction œcuménique de la Bible translates “He is always ready for”; New Jerusalem Bible and New International Version have “His mouth is full of”; Biblia Dios Habla Hoy has “his words hide (oppression and evil).” The idea expressed by Good News Translation and Traduction œcuménique de la Bible seems to be the most natural way to understand the phrase, but the meaning represented by New Jerusalem Bible and New International Version is also possible.
Mischief translates a word meaning trouble, misfortune, evil (it occurs in 7.14, 16, and also in verse 14, below). The word iniquity translates a word appearing many times in Psalms; in some instances it may have the specific meaning of a magic spell by means of which the speaker brings trouble on his victim. If iniquity is taken as a magic spell, it may be thought of as the result of a curse pronounced in line a, and in most cases will require a repetition of the curse term or its synonym as used in line a; for example, “His mouth is full of evil curses which cause people harm” or “With his mouth he curses people and binds them with his evil words.”
As translated in the Septuagint, verse 7a (in part) is quoted in Romans 3.14.
Quoted with permission from Bratcher, Robert G. and Reyburn, William D. A Handbook on the Book of Psalms. (UBS Helps for Translators). New York: UBS, 1991. For this and other handbooks for translators see here .