Revelation 6:9-11.

"When He 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 held. And the cried with a loud voice, saying, 'How long, O Lord, holy and true, until You judge and avenge our blood on those who dwell on the earth?' Then a white robe was given to each of them; and it was said to them that they should rest a little while longer, until both the number of their fellow servants and their brethren, who would be killed as they were, was completed."

God bless you.