Why do you have to study Daniel and Revelation together?
They must be studied together because the two books are so intertwined; studying Daniel requires going back to Revelation, and studying Revelation requires going back to Daniel. Both were written from outside Israel, and Revelation is described as a next of kin to Daniel.
Les explains that whenever you study Daniel, you have to go back to Revelation, and when you study Revelation, you have to go back to Daniel, because the two are so intertwined. He also notes that both were written from outside of Israel, and he ties in an analogy between the twelve apostles and Paul: Jesus chose the twelve within Israel's borders, but Paul was called on Gentile ground outside Damascus, setting him apart from the twelve. Revelation is such a next of kin with Daniel, and Les warns against lifting verses out of context.