Midrash su Isaia 24:13

The Chajjôth stand next to the throne of His glory and they do not know the place of His glory. The Chajjôth stand in awe and dread, in fear and trembling, and from the perspiration of their faces a river of fire arises and goes forth before Him, as it is said, "A fiery stream issued and came forth from before him…"(Dan. 7:10). And the wings of Gallizur the angel, who stands next to the Chajjôth, (are spread forth) so that the fire which consumes the fire of the angels should not burn (them). Two Seraphim stand, one on His right and one on His left, each one has six wings, with twain they cover their face so as not to behold the presence of the Shekhinah, with twain they cover their feet so that they should not be seen before the presence of the Shekhinah, || so that the standing of the foot of the calf might be forgotten. With twain do they fly, praising and reverencing, and they sanctify. One answers and another calls, one calls and another answers, and they say, "Holy, Holy, Holy, is the Lord of Hosts; the whole earth is full of his glory" (Isa. 6:3).