俱舍論疏 8.174

8.174

論「又影與光至謂二並生」，第三光、影相違未曾同處。現見鏡中光像在於影中，故知光像無實。

On the passage in the śāstra from "Furthermore, shadow and light" to "supposing that the two arise together": Third, light and shadow are mutually contradictory and have never occupied the same place. We directly see a luminous reflection in a mirror residing within a shadow; therefore we know that the luminous reflection is not real.