Rabbi Samson Raphael Hirsch - Horeb: A Philosophy of Jewish Law and Observances (1962)
There are probably no creatures that require more the protective Divine word against the presumption of man than the animals, which like man have sensations and instincts, but whose body and powers are nevertheless subservient to man. In relation to them man so easily forgets that injured animal muscle twitches just like human muscle, that the maltreated nerves of an animal sicken like human nerves, that the animal being is just as sensitive to cuts, blows, and beatings as man.
Thus man becomes the torturer of the animal soul—which has been subjected to him only for the fulfillment of humane and wise purposes—sometimes out of self-interest, at other times in order to satisfy a whim, sometimes out of thoughtlessness, yes, even for the satisfaction of crude satanic desire.
(יד) הוּא הָיָה אוֹמֵר, אִם אֵין אֲנִי לִי, מִי לִי. וּכְשֶׁאֲנִי לְעַצְמִי, מָה אֲנִי. וְאִם לֹא עַכְשָׁיו, אֵימָתַי:
(14) He [Rabbi Hillel] used to say: If I am not for me, who will be for me? And when I am for myself alone, what am I? And if not now, then when?