Whence is that knocking?
How is't with me, when every noise appals me?
What hands are here? Ha: they pluck out mine eyes.
Will all great Neptune's ocean wash this blood
 clean from my hand? No, this my hand will rather
The multitudinous seas incarnadine,
Making the green, one red.

- Macbeth

You can never go wrong with a Shakespeare entry in your commonplace book. Often the memorable lines aren’t the famous ones. Capture the ones that make you pause. That you need to re-read because they don’t make sense. Or because they’re striking.

Striking is a fine reason too.

William Shakespeare, Macbeth, ed. Sandra Clark and Pamela Mason, The Arden Shakespeare Third Series (London: Bloomsbury Arden Shakespeare, 2015), 2.2.66.