Revelation 6:9-10 NIV

9 When he opened the fifth seal, I saw under the altar the souls of those who had been slain because of the word of God and the testimony they had maintained.

References for Revelation 6:9

10 They called out in a loud voice, “How long, Sovereign Lord, holy and true, until you judge the inhabitants of the earth and avenge our blood?”

References for Revelation 6:10