Revelation 6:9 MSG

[9] When he ripped off the fifth seal, I saw the souls of those killed because they had held firm in their witness to the Word of God. They were gathered under the Altar, and cried out in loud prayers, “How long, Strong God, Holy and True? How long before you step in and avenge our murders?” Then each martyr was given a white robe and told to sit back and wait until the full number of martyrs was filled from among their servant companions and friends in the faith.