Revelation 6:9-11

9And when the Lamb opened the fifth seal, I saw under the altar the souls of those who had been slain for the word of God and for the testimony they had upheld. 10And they cried out in a loud voice, “How long, O Lord, holy and true, until You judge those who dwell upon the earth and avenge our blood?”

11Then each of them was given a white robe and told to rest a little while longer until the full number of their fellow servants, their brothers, were killed, just as they had been killed.