Thou best know’st
What torment I did find thee in; thy groans
Did make wolves howl and penetrate the breasts
Of ever angry bears: it was a torment
To lay upon the damned, which Sycorax
Could not again undo. It was mine art,
When I arrived and heard thee, that made gape
The pine and let thee out.

– William Shakespeare

The Tempest, Act 1, Scene 2. Unhappy with what he sees as Ariel’s ingratitude to him, Prospero reminds him that it was his powerful magic that undid the witch Sycorax’s spell and freed Ariel from his pine prison. Ariel’s groans of torment there made the wolves howl and penetrated the hearts of angry bears, he tells him. Prospero likes reminding his servant of how powerful he is.