俱舍論疏 18.39

18.39

論「若有害父至依止一故」，釋依一緣異。於一身上雖有恩、德二田，依止身一故成一逆罪。應說重逆。

The Śāstra states: "If one kills a father... because the physical support is one", explaining that though the conditions are different, they depend on one [support]. Although there are two fields of gratitude and merit in a single body, because the support body is one, it constitutes a single anantarya offense. It should be spoken of as a grave anantarya.