Henry IV Part 1 Lesson Plan

Why does Hotspur say, "While you live, tell truth and shame the devil!" (Act III, Scene I, Line 59)?

Hotspur says this in response to Glyndwr, who is boasting of his magical powers. Glyndwr is trying to get Hotspur to allow him to teach Hotspur how to develop his own magical practice, and do so soon so that they may defeat King Henry. Hotspur shows himself to be still connected to and identifying with the Christian statutes of England. He believes, because of his Christian belief, that he has power over the devil, and will shame the devil with the truth of Christ should Glyndwr attempt to summon him.

What does King Henry IV mean when he says, "He was but as the...