let us not plot against others….so by benefiting them we benefit ourselves

“Let us not plot against others, lest we injure ourselves. When we supplant the reputation of others, let us consider that we injure ourselves, it is against ourselves that we plot. For perchance with men we do him harm, if we have power, but ourselves in the sight of God, by provoking him against us. Let us not, then, injure ourselves. For as we injure ourselves when we injure our neighbors, so by benefiting them we benefit ourselves” (‘Hom. 14, in Phil.,’ Oxford transl.).

Source: http://biblehub.com/proverbs/26-27.htm