Oecumenius — on Rev 11:16-17 (Commentary on Revelation)

“When this voice arose, the elders worshiped God, also offering their own thanksgiving, saying, "We give thanks to you, Lord God Almighty, who is and who was." The phrase "who is" is properly attributed to the Holy Trinity, and "who was," although primarily said concerning the Father, is also applied to the Son, for the Father, the Son, and the Holy Spirit all exist eternally. Thus, the term "who was" is rightly spoken of the Father, the Son, and the Holy Spirit. Therefore, the thanksgiving of the elders is dedicated to the Holy Trinity. That you say you have taken your great power and your kingdom from those on earth, and that you alone now reign; but concerning the earthly kingdom that is perishing, it is understandable that the nations became angry, as their dominion was overthrown, referring to the orders of both the demons and the unbelieving men.”