俱舍論頌疏論本 17.102

17.102

非餘扇搋等，少恩少羞恥者，釋扇搋等雖殺父母，無無間業，謂彼父母於彼少恩少愛念故，彼於父母慚愧心微，無重恩故，故無無間。由此道理，鬼及傍生雖害父母，亦無無間。又大德說：「傍生類中，覺慧分明亦成無間，如聰慧馬。曾聞有馬，人貪其種，令與母合，覺知是母，便即羞死。」又若人害非人父母，不成逆罪，心境劣故（此據人從非人生也）。

"Not in the others, nor in ṣaṇḍhas and so forth, due to slight gratitude and slight shame" explains why ṣaṇḍhas and so forth, even if they kill their parents, do not [commit] immediate karma: because those parents show slight kindness and slight affection toward them, and their sense of shame and conscience toward their parents is weak, lacking great gratitude; hence, there is no immediate [karma]. By this reasoning, although ghosts and animals may kill their parents, they also have no immediate [karma]. Furthermore, the Bhadanta says: "Among animals, those whose discernment is distinct also incur the immediate, like an intelligent horse. It was once heard that there was a horse whose owner coveted its breed and caused it to mate with its mother; recognizing that it was its mother, it immediately died of shame." Furthermore, if a human kills non-human parents, it does not constitute the heinous crime, because the mind and the object are inferior (this is said with regard to a human born from non-humans).