How long, O Lord
Lord is δεσπότης [despotēs] which emphasizes His ownership of the saints, as a master has slaves,1 or a ruler over a household (Tit. Tit. 2:9).2 Let us always keep in mind that He can do whatever He desires with His sheep. In this case, He allows their slaughter as a testimony to their faith and the evil unfolding below which will finally be judged.
judge and avenge
When God finally tramples the winepress of His wrath it is described as the day of vengeance, for the year of My redeemed has come (Isa. Isa. 63:3-4). This then, is the judgment associated with the fifth sealthat petition of God by the martyred saints seals the fate of those who put them to death. One of the duties of the Goel , the nearest of kin, was to avenge the blood of the family member who had been murdered (Num. Num. 35:19-21; Deu. Deu. 19:6; Jos. Jos. 20:3). See commentary on Revelation 5:9.
dwell on the earth
Their persecutors appear to be currently living on the earth which argues for understanding these as recent martyrs from the times described by the seals. This phrase denotes the earth dwellers and has significance far beyond merely designating people who happen to be living upon the earth. In this book, it takes on a soteriological and eschatological sense as a technical phrase describing those in the end times who refuse salvation, persecute the saints, and continue to blaspheme God in the midst of judgment (Rev. Rev. 3:10+; Rev. 6:10+; Rev. 11:10+; Rev. 12:12+; Rev. 13:8+, Rev. 13:12+, Rev. 13:14+; Rev. 14:6+; Rev. 17:8+).3 These are the ones being tested by this time of trial from God (Rev. Rev. 3:10+) and rejoice when Gods two witnesses are killed (Rev. Rev. 11:10+). It is they who are subject to the wrath of both God and the devil (Rev. Rev. 12:12+) and who will be deceived into worshiping the beast (Rev. Rev. 13:12+, Rev. 13:14+). Even though an angel preaches the everlasting gospel to each one (Rev. Rev. 14:6+), they continue in their rejection of God to the end. Therefore, their names are not written in the Book of Life (Rev. Rev. 17:8+). See Book of Life.
1 Frederick William Danker and Walter Bauer, A Greek-English Lexicon of the New Testament and Other Early Christian Literature (Chicago, IL: University of Chicago Press, 2000), 176.
3 Them that dwell on the earth is a semi-technical designation for mankind in its hostility to God.Robert H. Mounce, The Book of Revelation (Grand Rapids, MI: William B. Eerdmans Publishing Co., 1977), 159.