Isaiah - Chapter 14
No Fallen Angel
G-d will destroy Babylonia, then have mercy on the Jews and return them to their land, where they will rule over their former oppressors. On that day, the Jewish people will have relief from their sorrows. They will say to the Babylonians that G-d has broken the staff of those who would oppress others. Even the trees will rejoice with the downfall of Nebuchadnezzar, since they will no longer be felled for war.
Just as those above the ground feared Nebuchadnezzar, those below the ground (in the grave, possibly in Hell) will likewise dread his coming. But they will realize that Nebuchadnezzar no longer has any power. He has fallen from his lofty station to maggots and worms. The one who intended to ascend to the highest heights has been brought down to the pit (again, the grave, or possibly Hell). People will look at him in disbelief. "This is what we were all so afraid of? All the kings lay in honor, but he was cast out of his grave." (The commentators quote the Seder Olam that Nebuchadnezzar's body was exhumed and dragged as a rebellion against his decrees.)
G-d says, "I will rise against Babylonia and cut off his descendants" (including Belshazzar and Vashti). The land will be "swept with the broom of destruction." G-d has decreed it and nobody can thwart His plans.
This prophecy was made in the year King Achaz died (and the righteous Chizkiyahu assumed the throne): The Philistines should not rejoice that Achaz is dead, since his offspring will do even more damage to them. Israel will dwell safely, while the Philistines will starve, then Israel will destroy the survivors. Messengers will announce that G-d has founded Zion (Jerusalem) and the remnants of the "lost" Tribes will take shelter there.
Some view verse 12, "How you have fallen from Heaven, glowing morning star" to refer to a "fallen angel," whom they call Lucifer. Of course, this is not consistent with the text, nor with Jewish philosophy. The whole section is part of a parable beginning with verse 4, describing the downfall of the king of Babylonia. (It says so straight out: "You shall carry this parable about the king of Babylonia.") Additionally, angels lack the free will necessary to rebel; they are mere automatons, programmed to do G-d's will. In Judaism, one might as well speak of a fallen toaster, since both have the same capacity to rebel against G-d. (We will address the Jewish concept of Satan in the Book of Job, IY"H.)