Give me that man
That is not passion’s slave, and I will wear him
In my heart’s core, ay, in my heart of heart,
As I do thee.

– William Shakespeare

Hamlet, Act 3, Scene 2. Hamlet warmly praises Horatio, just before The Mousetrap play-within-a-play is about to begin. Hamlet trusts his friend so much that he confides to him the secret purpose of the play. It contains a scene mirroring the circumstances of Hamlet’s father’s murder, as claimed by the Ghost. Hamlet asks Horatio to watch Claudius’ reaction to see if he shows any signs of guilt.