淨名經集解關中疏 2.191

2.191

現於涅槃而不斷生死　九涅槃。肇曰。現身涅槃而方入生死。自上所列於菩薩皆為非道而處之無礙。乃所以為道。故曰。通達佛道。

"He manifests in nirvāṇa yet does not sever birth and death." Ninth, nirvāṇa. Zhao says: "He manifests his body in nirvāṇa, yet precisely enters birth and death. All those listed above are 'not the path' for a bodhisattva, yet dwelling in them without obstruction is precisely how they become the path. Hence it is said: 'penetrating the Buddha path.'"