涅槃經遊意 1.206

1.206

行有三雙：生死涅槃明行解，生死在無常為行解，涅槃樂為行。此八行解乃得涅槃四德也。

Practices have three pairs: practice and understanding are clarified regarding saṃsāra and nirvāṇa; saṃsāra abiding in impermanence constitutes practice and understanding, and the bliss of nirvāṇa constitutes practice. Only through these eight practices and understandings does one attain the four virtues of nirvāṇa.