Song of Trust
Chapter 26 is a song about the end time. "In that day" (verse 1) means the Day of the Lord—but the bright part of it beyond the gloom. Salvation is at last coming to God's people, which will lead to the salvation of all people.
Several themes are addressed. The chapter begins by emphasizing righteousness and trust in God. Look again at verse 3. What a wonderful promise this is. If we trust in God, come what may, we will have perfect peace—inner peace of mind or, as Paul puts it, "the peace of God that surpasses all understanding" (Philippians 4:7).
The chapter goes on to address the punishment and reform of the wicked.
Verse 19 describes the resurrection. "Some argue that this is a figurative application of the idea of resurrection. But there could have been no figure of speech if no belief that 'their bodies will rise' existed in ancient Israel. And what a wonder this is. Storms of judgment may sweep over our earth. Wars may devastate, and disease may ravage. Famines may decimate the land, while starvation stalks our families. There are indeed dread fates that are to be feared. But these are not history's last words! At the end of history—both the history of nations, and the personal history of each individual—the shout of God's promise echoes. 'Your dead will live; their bodies will rise!' What a truth to hold fast in troubled times" (Bible Reader's Companion, note on verse 19).
Verses 20-21 mention God directing His people to take refuge "until the indignation is past." This ties in with other verses related to a place of protection for some of God's saints during the final days before Christ's return (see Zephaniah 2:1-3; Revelation 12:14). God will also preserve alive a remnant of the physical descendants of Israel.
Leviathan (Isaiah 27:1) is mentioned in several places in Scripture (compare Job 41; Psalm 74:14; Psalm 104:26). It may be a literal sea creature, but here, as in other places, it is apparently a reference to Satan, the serpent and dragon of Revelation 12, and the "beast from the sea" (Revelation 13), the resurgent gentile empire of the last days, the heads of which are portrayed as emerging from Satan (Revelation 12:3; Revelation 13:1-2).
Deliverance of Israel
Finally, God turns to the wonderful restoration of national Israel that's coming. His vineyard was forsaken (Isaiah 5:1-5). But now He will tend it again (Isaiah 27:2-4). The great trumpet will call the exiles of Israel to return to the land of Abraham, Isaac and Jacob. Their emaciated and war-ravaged population, dwindled down to a small fraction of their former numbers, will again begin to blossom and grow (verse 6)—in the very best environment possible.