Revelation 6:9-11

When the Lamb broke open the fifth seal, I saw gathered under the altar the souls of those who had been slain because of the Word of God and because they had the testimony of the Lamb. They cried out with a loud voice, saying, “Sovereign Lord, holy and dependable, how long before you judge those who live on the earth and vindicate our blood on them?” Each one was given a glistening white robe. And they were told to rest a little longer, until the full number was fulfilled of both their fellow servants and brothers and sisters who were going to be killed just as they had been.