No, no, they do but jest, poison in jest; no offence i' th' world.
Act III, Scene 2 · Hamlet
Context
When Claudius asks if there is anything offensive in the play, Hamlet insists it is harmless, saying the poison is only 'in jest' and means no offense.
Analysis
Hamlet's repetition of 'jest' and 'offence' (which also meant 'crime' in Elizabethan English) plays on the gap between theatrical fiction and real guilt—he pretends the staged murder is mere entertainment while using it to accuse Claudius of actual murder. The phrase 'poison in jest' is a perfect oxymoron: poison cannot be playful, just as Hamlet's 'jest' is no joke. This double-speak forces Claudius to either ignore the obvious parallel or admit he recognizes himself in the murderer.
Essay Tip
Use this to argue that Hamlet's verbal strategy is entrapment through irony—by insisting the play is harmless, he dares Claudius to contradict him and thereby confess.