維摩經玄疏 2.101

2.101

答曰：《大涅槃經》云「不生不生，名大涅槃。以修道得故，故不可說」，豈如諸大乘論師，偏執定說也。今以因緣故，亦可得說者。若解四悉檀意，如前異說，皆大利益眾生，興顯佛法也。

Answer: The Nirvāṇa Sūtra says: 'Unarisen and unarising is called great nirvāṇa. Because it is attained through cultivating the path, it is ineffable.' How could it be like the masters of Mahāyāna treatises who cling exclusively to a fixed explanation? That it can now also be explained is due to causes and conditions. If one understands the intent of the four siddhāntas, then the differing explanations mentioned above all greatly benefit sentient beings and cause the Buddhadharma to flourish and become manifest.