John says that the souls he saw were “of those who had been slain for the word of God and for the witness they had borne.” The first horse had gone out into God’s world with the gospel of redemption and as a result people had come to faith (see Acts 2:41; Acts 4:4; Acts 5:14; Acts 6:7; etc.). But just as Jesus was hated and killed, so too some of his saints were hated and killed (see John 15:18–25). We may think of people like Stephen (Acts 7:60), the ones Saul imprisoned and killed in his hatred of Jesus Christ (Acts 9:1, Acts 26:10–11), and the murder of James (Acts 12:2) and Antipas (Revelation 2:13). They had embraced the Saviour and were not ashamed of him, even sealing their devotion to Jesus Christ with their own blood.
9 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 witness they had borne.