Against Heresies: Book IV
Chapter 3: Response to the Criticisms of the Gnostics. We should not assume that the true God can be altered or cease to exist just because the heavens, which are his throne, and the earth, his footstool, will eventually disappear
Again, regarding their malicious claim that if heaven is indeed the throne of God, and earth His footstool, and if it is stated that heaven and earth will pass away, then when these pass away, the God who sits above must also pass away, and therefore He cannot be the God who is over all; first, they do not understand what it means that heaven is His throne and earth His footstool. They do not know what God is, imagining Him to sit like a man and be contained within limits, but not as one who contains all.
They are also unaware of the meaning of the passing away of heaven and earth; yet Paul was not ignorant of it when he said, “For the form of this world passes away.” Furthermore, David answers their question, stating that when the form of this world passes away, not only shall God remain, but His servants will too, as he expresses in the 101st Psalm: “In the beginning, You, O God, have founded the earth, and the heavens are the works of Your hands.
They shall perish, but You shall endure, and all shall grow old like a garment; and like clothing You will change them, and they shall be changed: but You are the same, and Your years will not fail. The children of Your servants shall continue, and their descendants will be established forever;” clearly showing what things pass away, and who it is that endures forever—God, along with His servants. Similarly, Isaiah says: “Lift up your eyes to the heavens, and look at the earth below; for the heavens shall vanish like smoke, and the earth shall grow old like a garment, and those who live on it shall die in like manner.
But my salvation shall be forever, and my righteousness shall not pass away.”