Revelation 6:9-11 - The Fifth Seal
9 And when he had 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 which they had borne: 10 and they cried with a loud voice, saying: How long, Sovereign, holy and true, dost thou not judge and avenge our blood on them that dwell on the earth? 11 And a white robe was given to each of them: and it was said to them, that they should yet rest for a time, till the number of their fellow-servants,, and of their brethren, who should be killed as they had been, should be completed.