They cried out: that is, they shouted, not wept.
O Sovereign Lord: this Greek word was generally used to refer to an owner of slaves, but in this context it is used as a title meaning “Powerful Master” or “Powerful (or, Almighty) God.” Elsewhere it appears in Luke 2.29 (RSV “Lord”); Acts 4.24; 2 Peter 2.1; Jude 4, where it has been translated as either “Lord,” “Sovereign Lord,” or “Master.” In the Luke and Acts references it refers to God, and in 2 Peter to Christ. Here in Revelation it is a title for God.
Holy and true: see 3.7, where these qualities are ascribed to Christ. But in this verse God is described as holy or pure, and is true or trustworthy.
How long: this cry of the persecuted people of God is a request, or demand, that God act at once: “Why do you delay…?” or “Don’t wait any longer…!” or “Why do you wait so long?” (see similar cries in Psa 6.3; 13.1-2; 35.17; Isa 6.11; Zech 1.12). In many languages this idea will be expressed as “Please don’t wait any longer.”
Judge and avenge our blood on those who dwell upon the earth: judge may also be expressed as “decide the guilt of,” “decide whether a person is guilty or innocent,” or idiomatically, for example, as “untie the words of” (Yapese), or “sing a (court) case against” (Chewa). In heaven the martyrs ask that God declare the guilt of the murderers and punish them. To avenge means to do what is needed to get even with the guilty ones; in this context it is some form of punishment, if not death. Our blood here means “our death,” “our murder” (see 1.5). And those who dwell upon the earth, although a phrase that seems to include all the people in the world, is here a reference to those who had executed these Christians (see comments on 3.10).
An alternative translation model for this verse is:
• These spirits shouted in a loud voice saying, “Almighty God, you are pure and trustworthy! Please don’t wait any longer to condemn and punish those people on earth who killed us.”
Quoted with permission from Bratcher, Robert G. and Hatton, Howard A. A Handbook on The Revelation to John. (UBS Handbook Series). New York: UBS, 1993. For this and other handbooks for translators see here .