Hath the Lord covered; rather, doth … cover. The daughter of Zion; i.e. Jerusalem. Cast down from heaven. Here and in Matthew 11:28 we have a parallel to Isaiah 14:12, where the King of Babylon is compared to a bright star.
"Cast down" whither? Into the "pit" or dungeon of Hades (Isaiah 14:15). The beauty of Israel; i.e. Jerusalem, exactly as Babylon is called "the proud beauty [or, 'ornament'] of Chaldea" (Isaiah 13:19).
His footstool; i.e. the ark (Psalms 132:7), or perhaps the temple as containing the ark (1 Chronicles 28:2; Psalms 99:5).