Revelation 6:9-11

9And when it opened the fifth seal, I saw underneath the altar the souls of them that had been slain for the word of 1God, and for the testimony which they held;

10and they cried with a loud voice, saying, How long, O sovereign Ruler, holy and true, dost thou not judge and avenge our blood on them that dwell upon the earth?

11And there was given to them, to each one a white robe; and it was said to them that they should rest yet a little while, until both their fellow-bondmen and their brethren, who were about to be killed as they, should be fulfilled.