The beginning of verse 7 should be marked by a contrast: the enemies and the cities perish, but the LORD remains forever.
The LORD is again pictured in his role as ruler and judge of all people. Sits enthroned translates the verb “to sit”; see comments on “thy seat” in 7.7. Here the LORD’s throne is thought of as being in heaven (contrast with verse 11, below). The verb “to sit” may have the more general sense of “dwell, abide, remain,” and that is how the Septuagint has translated it here; so New Jerusalem Bible “But the LORD abides forever.”
The verb translated he has established means “make firm, set up”–see 7.9; 8.3.
For judgment means “in order to judge (humankind).”
Verses 7-8 are a semantic unit in which the images of throne and judgment in verse 7 are carried forward into verse 8. In the latter, as in verse 6, there is a focusing taking place. This focusing is upon the manner of God’s judgment, with righteousness. In order to make clear the relation of verse 8 to verse 7, a connective is needed in English; for example, verse 8 can begin with “In fact, God rules the world with righteousness” or “Furthermore, God judges….” Another way is to begin verse 7 “But not only is the LORD on his throne” and begin verse 8 “he even judges the world…” or “he also rules the world….”
The two lines in verse 8 are parallel and synonymous; the two verbs for “to judge” are those used in 7.8; the world is expanded with the peoples; and righteousness and equity are identical in meaning. A common English idiom for saying the two is “fairly and squarely.” Righteousness and equity are expressed idiomatically in some languages in a negative manner; for example, “he does not judge with two mouths” or “he does not judge with money.” Rendered positively, “he judges with a true word” or “he judges with one mouth.”
Some translations (New English Bible, Biblia Dios Habla Hoy, New International Version, New Jerusalem Bible) have the two verbs in verse 8 in the future tense, “He will rule … he will judge.” This may be followed by the translator, but the present tense seems preferable.
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 .