The Metaphysics of Morals by Immanuel Kant Chapter 2 Page 99

spring which can give actions a moral worth. Our own will, so far as we suppose it to act only under the condition that its maxims are potentially universal laws, this ideal will which is possible to us is the proper object of respect; and the dignity of humanity consists just in this capacity of being universally legislative, though with the condition that it is itself subject to this same legislation.

The Autonomy of the Will as the Supreme Principle of Morality

Autonomy of the will is that property of it by which it is a law to itself (independently of any property of the objects of volition).

The principle of autonomy then is: “Always so to choose that the same volition shall comprehend the maxims of our choice as a universal law.”