Musar for Bava Metzia 146:14

לעולם בהם תעבודו . This rule of owning Gentile slaves permanently (25,46) (as opposed to Jewish servants), is rooted in the status of Canaan as a slave since the days of Noach. The status was conferred upon him in retaliation for his having uncovered the nakedness of his grandfather. The curse is connected with the original pollutant introduced into Eve as a result of the serpent having mated with her. Israel are called אחיך, having been created in the צלם אלוקים, the image of G–d. When one does not behave like a "brother," אחיך, by such deeds as behooves a person created in the image of G–d, then the Torah will apply the epithet ובאחיך to such a person.