“ In a word, the moral law demands obedience, from duty not from predilection, which cannot and ought not to be presupposed at all. ”
 Immanuel Kant, Critique of Practical Reason (1788). copy citation

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“Now if these conceptions are to become subjectively practical, we must not rest satisfied with admiring the objective law of morality, and esteeming it highly in reference to humanity, but we must consider the conception of it in relation to man as an individual, and then this law appears in a form indeed that is highly deserving of respect, but not so pleasant as if it belonged to the element to which he is naturally accustomed; but on the contrary as often compelling him to quit this element, not without self-denial, and to betake himself to a higher, in which he can only maintain himself with trouble and with unceasing apprehension of a relapse. In a word, the moral law demands obedience, from duty not from predilection, which cannot and ought not to be presupposed at all. Let us now see, in an example, whether the conception of an action, as a noble and magnanimous one, has more subjective moving power than if the action is conceived merely as duty in relation to the solemn law of morality.” source