This, then, is evident, That A MAN IS NOT AT LIBERTY TO WILL, OR NOT TO WILL, ANYTHING IN HIS POWER THAT HE ONCE CONSIDERS OF: liberty consisting in a power to act or to forbear acting, and in that only.
 John Locke, An Essay Concerning Human Understanding (1689). copy citation

Context

“So that, in respect of the act of willing, a man is not free: liberty consisting in a power to act or not to act; which, in regard of volition, a man, has not.
24. Liberty is freedom to execute what is willed.
This, then, is evident, That A MAN IS NOT AT LIBERTY TO WILL, OR NOT TO WILL, ANYTHING IN HIS POWER THAT HE ONCE CONSIDERS OF: liberty consisting in a power to act or to forbear acting, and in that only. For a man that sits still is said yet to be at liberty; because he can walk if he wills it. A man that walks is at liberty also, not because he walks or moves; but because he can stand still if he wills it.” source