首楞嚴義疏注經 7.216

7.216

Enemies and rivals mutually taking vengeance, the chain never ceases. Lodging in the closest intimacy of father and child, they bring forth the utmost enmity of slaughter—how could this not be monstrous? At the initial birth when lodging in form, there is mutually thought and affection, hence it is said 'forming out of non-thoughtlessness.' Later when grown large, the parents are eaten, hence it is said 'thoughtless.' The dirt-owl and the mirror-breaking bird, adopting a clod of earth and brooding on poisonous fruit, their sons and grandsons mutually completing and succeeding one another—it is karma that causes this, not nature.