肇論新疏 1.185

1.185

何者？果不俱（兼也）因，因（由也）因而果。因因而果，因不昔滅；果不俱因，因不來今。不滅不來，則不遷之致明矣。

Why is this? The fruit does not accompany (hold concurrently with) the cause, and the cause gives rise to (stems from) the fruit. Because the cause gives rise to the fruit, the cause does not cease in the past; because the fruit does not accompany the cause, the cause does not come into the present. Since it does not cease and does not come, the principle of immutability is clear.