維摩經玄疏 6.28

6.28

First, clarifying the true mark of dharma-nature in terms of unshared prajñā under the distinctive teaching: severing the two obstructions, leaving behind the two extremes of birth-and-death and nirvāṇa, it distinctively takes the principle of the non-empty, the intrinsically pure mind, and the principle of the tathāgatagarbha as the true mark of dharma-nature; thus the śrāvakas in the assembly were as if deaf and mute. It is like breaking ore to obtain genuine gold, which differs from crystal: genuine gold cannot be destroyed and can be made into various vessels at will; crystal is easily broken and cannot be refashioned into various vessels.