法苑珠林 90.19

90.19

又成實論云。不為修善故食則唐養怨賊。亦壞施主福損人供養。如是不應食人之食。

Furthermore, the Tattvasiddhi-śāstra says: 'If one eats not for the sake of cultivating goodness, then one futilely feeds an adversarial thief, and also ruins the donor's merit and harms people's offerings. In this manner, one should not eat the food of others.'