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 Revelation 4:11 (John 20:28). On δεσποτης (correlative of δουλος) see Luke 2:29. Here (alone in the Apocalypse) it is applied to God as in Luke 2:29; Acts 4:24, but to Christ in Judges 1:4; 2. Peter 2:1.

The holy and true (ο αγιος κα αληθινος). See Revelation 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 Revelation 19:2 and see it also in Luke 18:7, "a passage which goes far to answer many questions in theodicy" (Swete). We find εκδικεω, late compound, used with εκ as here in Deuteronomy 18:19; 1. Samuel 24:13, but with απο in Luke 18:3. For επ της γης (upon the earth) see Revelation 3:10.