A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown  at sacred-texts.com
psa 94:1The writer, appealing to God in view of the oppression of enemies, rebukes them for their wickedness and folly, and encourages himself, in the confidence that God will punish evildoers, and favor His people. (Psa. 94:1-23)
God's revenge is His judicial infliction of righteous punishment.
show thyself--(Compare Margin).
psa 94:2Lift up thyself--or, "Arise," both figures representing God as heretofore indifferent (compare Psa 3:7; Psa 22:16, Psa 22:20).
psa 94:3In an earnest expostulation he expresses his desire that the insolent triumph of the wicked may be ended.
psa 94:5thy people [and] thine heritage--are synonymous, the people being often called God's heritage. As justice to the weak is a sign of the best government, their oppression is a sign of the worst (Deu 10:18; Isa 10:2).
psa 94:7Their cruelty is only exceeded by their wicked and absurd presumption (Psa 10:11; Psa 59:7).
psa 94:8ye brutish--(Compare Psa 73:22; Psa 92:6).
psa 94:9The evidence of God's providential government is found in His creative power and omniscience, which also assure us that He can punish the wicked in regard to all their vain purposes.
psa 94:12On the other hand He favors though He chastens, the pious, and will teach and preserve them till the prosperous wicked are overthrown.
psa 94:14This results from His abiding love (Deu 32:15), which is further evinced by His restoring order in His government, whose right administration will be approved by the good.
psa 94:16These questions imply that none other than God will help (Psa 60:9),
psa 94:17a fact fully confirmed by his past experience.
dwelt in silence--as in the grave (Psa 31:17).
psa 94:19my thoughts--or, anxious cares.
psa 94:20throne--power, rulers.
iniquity [and] mischief--both denote evils done to others, as Psa 94:21 explains.
psa 94:22Yet he is safe in God's care.
defence-- (Psa 59:9).
rock of . . . refuge-- (Psa 9:9; Psa 18:2).
psa 94:23bring . . . iniquity--(Compare Psa 5:10; Psa 7:16).
in their . . . wickedness--while they are engaged in evil doing.