The Metaphysical Elements of Ethics by Immanuel Kant Chapter 8 Page 5

the law does not command this internal action in the human mind itself, but only the maxim of the action, namely, that we should strive with all our power that for all dutiful actions the thought of duty should be of itself an adequate spring.

(2) HAPPINESS OF OTHERS as an end which is also a duty

(a) Physical Welfare. Benevolent wishes may be unlimited, for they do not imply doing anything. But the case is more difficult with benevolent action, especially when this is to be done, not from friendly inclination (love) to others, but from duty, at the expense of the sacrifice and mortification of many of our appetites. That this beneficence is a duty results from this: that since our self-love cannot be separated from the need to be loved by others (to