Chapter 26 of the Book of the Prophet Isaiah, to which the verses you are inquiring about belong, contains a unified poetic work, the "Hymn of Isaiah." It was composed by an unnamed follower of the prophet Isaiah, who lived in the mid-6th century BC and is traditionally referred to as Deutero-Isaiah. This hymn...
Chapter 26 of the Book of the Prophet Isaiah, to which the verses you are inquiring about belong, contains a unified poetic work, the "Hymn of Isaiah." It was composed by an unnamed follower of the prophet Isaiah, who lived in the mid-6th century BC and is traditionally referred to as Deutero-Isaiah. This hymn (which is widely used, incidentally, in Orthodox liturgical worship) is part of a larger text (chapters 24-27), the so-called Apocalypse of Isaiah. Through poetic means, employing historical analogies characteristic of his tumultuous era, Deutero-Isaiah depicts God's impending victory over sin and death. As in other texts by Deutero-Isaiah (who authored the entire second half of the Book of Isaiah, beginning with chapter 40), historical cataclysms here (in particular, the wars between the Persian and Babylonian empires) serve as prefigurations of God's intervention in history. This also applies to the verses in question.
The differences between the texts of the Septuagint and the Vulgate, as well as between the Slavonic and Russian Bibles, can be attributed to the fact that in ancient Israel there were several versions of the text, preserved and transmitted by different groups of scribes. The ancient Hebrew text, preserved in the Masoretic version, was transmitted by the scribes of Jerusalem; the Vulgate follows it, and the Russian Synodal translation was made from it. The Alexandrian Jews preserved and transmitted their own version of the text (perhaps even more than one); the Greek translation (the Septuagint) was made from this version. The Slavonic text was primarily translated from the Greek (especially those passages incorporated into liturgical worship) and was partially (though not entirely) revised according to the Vulgate in the 15th century.
26 A song of praise and confidence in God, for the blessings of righteousness, judgments on their enemies, and favour to his people: their chastisement, repentance, and hope, Isa 26:1-21.
26:19 Thy - The prophet here turns his speech to God's people, and gives them a cordial in their distress. Thy dead men are not like those, ver. Isa 26:14, for they shall not live; but thine shall live. You shall be delivered from all your fears and dangers. My dead body - As I myself, who am one of these dead men, shall live again; you shall be delivered together with me. Awake - Out of your sleep, even the sleep of death, you that are dead and buried in the dust. Thy dew - The favour and blessing of God upon thee. The dew - Which makes them grow and flourish.