A.T. Robertson Commentary Revelation 6:10

"and they cried with a great voice, saying, How long, O Master, the holy and true, dost thou not judge and avenge our blood on them that dwell on the earth?" — Revelation 6:10 (ASV)

How long (εως ποτε). "Until when." Cf. Matthew 7:17; John 10:24.

O Master (ο δεσποτης). Nominative articular form, but used as vocative (δεσποτα) as in 4:11 (John 20:28). On δεσποτης (correlative of δουλος) see Lu 2:29. Here (alone in the Apocalypse) it is applied to God as in Lu 2:29; Acts 4:24, but to Christ in Jude 1:4; 2 Peter 2:1.

The holy and true (ο αγιος κα αληθινος). See 3:7 for these attributes of God.

Avenge our blood on them that dwell upon the earth (εκδικεις το αιμα ημων εκ των κατοικουντων επ της γης). This same idiom in 19:2 and see it also in Lu 18:7f. , "a passage which goes far to answer many questions in theodicy" (Swete). We find εκδικεω, late compound, used with εκ as here in De 18:19; 1 Samuel 24:13, but with απο in Lu 18:3. For επ της γης (upon the earth) see 3:10.