Revelation 4:8 - Matthew Poole's English Annotations on the Holy Bible

And the four beasts had each of them six wings about him: the seraphims in Isaiah's vision, Revelation 6:2, had so; there their use is declared, with twain he covered his face, with twain his feet, and with twain he did fly. If we understand all the wings here for flight, they signify the readiness of God's ministers to move every way that God will send them: if we understand them as interpreted by Isaiah 6:2, they signify their various graces, their fear, dread, and reverence of God; their humility and modesty; their agility, or readiness to obey all the commands of God. And they were full of eyes within: this denotes that large measure of knowledge, and diligence, and watchfulness, which should be in a minister of Christ. And they rest not day and night, saying, Holy, holy, holy, Lord God Almighty: this was the song of the seraphims, Isaiah 6:3, and shows how much it should be the care of ministers to make God known in all his attributes, his holiness especially, and his power. Which was, and is, and is to come; and his eternity and simplicity, as he is the same yesterday, to-day, and for ever, without variableness or shadow of change.