維摩經玄疏 5.142

5.142

Eighth, analogously correlating the three kinds of nirvāṇa: first, naturally pure nirvāṇa; second, completely pure nirvāṇa; third, expediently pure nirvāṇa. The name 'completely pure' is not yet seen in the sūtra text. A master of the Daśabhūmika said: ''Expediently pure nirvāṇa' is derived from the meaning of the sūtra text, establishing responsive and transformed nirvāṇa to make the three nirvāṇas. If one takes the convenient sense, completely pure is convenient; if one takes 'expedient means', expediently pure is convenient.' Now we explain that the liberation of the true nature is naturally pure nirvāṇa; the liberation of real wisdom is completely pure nirvāṇa; the liberation of expedient means is expediently pure nirvāṇa.