妙法蓮華經玄義 9.35

9.35

Sixth, skillfully discerning the aids to the path: Contemplating birth and death as identical to nirvāṇa, the form aggregate of birth and death across the ten realms is neither pure nor impure, up through the consciousness aggregate being neither permanent nor impermanent. Being able to break through the eight inversions is the four applications of mindfulness of dharma-nature; within these applications of mindfulness are replete the aids to the path, the three liberations, and all dharmas. Furthermore, knowing that nirvāṇa is itself birth and death reveals the four withered trees; knowing that birth and death is itself nirvāṇa reveals the four flourishing trees; knowing that birth and death and nirvāṇa are non-dual is the single real truth, neither withered nor flourishing, abiding in the great nirvāṇa.