2 Above him were seraphim, each with six wings: With two wings they covered their faces, with two they covered their feet, and with two they were flying.
References for Isaiah 6:2
3 And they were calling to one another: “Holy, holy, holy is the LORD Almighty; the whole earth is full of his glory.”
4 At the sound of their voices the doorposts and thresholds shook and the temple was filled with smoke.