The clause beginning with the word “for” provides the reason for the elders' thanksgiving: “For you have taken your great power and begun to reign.” It is striking that in their earlier sayings, the twenty-four elders emphasized that the Lord was worthy to receive glory and honour and power (Revelation 4:11) and to open the seals of the scroll (Revelation 5:9). Fulfilling his worthiness lay in the future. In the interim after those first two songs, the exalted Lamb has opened the seven seals (Revelation 6:1–8:1) and prompted the blowing of the seven trumpets (Revelation 8:2–11:15). All they have seen has confirmed the declaration of the loud voices of heaven, and it is this that prompts the elders’ thanksgiving prayer. In the words of Revelation 11:17, Christ has taken his great power and begun to reign.
17 saying, “We give thanks to you, Lord God Almighty, who is and who was, for you have taken your great power and begun to reign.