We've talked a lot about how the prophets condemned the sins of Israel and Judah, and prophesied exile as punishment: Israel would fall to Assyria and Judah to the Babylonians.  But in the later parts of their prophesies, both Jeremiah and Ezekiel deal with people already in captivity and their prophesies turn to hope.  And a major part of that hope is a renewed covenant God promises to his people. 
Scripture: Jeremiah and Ezekiel