(I,iii) Hamlet:

This above all: to thine own self be true, And it must follow, as the night the day, Thou canst not then be false to any man.

(II,ii) Hamlet:

Why, then, ’tis none to you, for there is nothing either good or bad, but thinking makes it so. To me it is a prison.

(III,iii) King Claudius:

My words fly up, my thoughts remain below: Words without thoughts never to heaven go.