Tell truth and shame the devil

William Shakespeare, Henry The Fourth, Part I Act 3, scene 1, 52–58

Glendower: I can call spirits from the vasty deep.

Hotspur: Why, so can I, or so can any man;
But will they come when you do call for them?

Glendower: Why, I can teach you, cousin, to command
The devil

Hotspur: And I can teach thee, coz, to shame the devil—
By telling the truth. Tell truth and shame the devil.