大乘起信論義記 2.57

2.57

Regarding "empty in accordance with reality" (tathā-śūnya): this means that within reality, it is empty of delusional defilements, hence called "empty in accordance with reality"; it does not mean that reality is itself empty. This is "emptiness of reality," a tatpuruṣa compound. Because delusion is empty, it can thereby reveal the true principle; hence it is said to "reveal the real." Therefore the Madhyāntavibhāga says: "The existence of the non-existence of grasper and grasped, and the non-existence of the grasper and grasped, is called the mark of emptiness."