法華論疏 1.116

1.116

謂八九十三地無相行寂靜清淨故者，六地定不淨，七地二國中間亦淨不淨，八地已上名定清淨。七地無相有功用故未寂靜；八地無相無功用故寂靜，寂靜故清淨。又亦得無相為八地、寂靜為九地、清淨者謂十地，以十地於惑智二障中或障結習纏盡，故名清淨。

Regarding "because above the eighth stage, the three stages are signless practice, tranquil and pure": the sixth stage is definitely not pure; the seventh stage, being intermediate between the two realms, is also partly pure and partly not pure; from the eighth stage upward, it is called definitely pure. The seventh stage is signless with effort, and hence not yet tranquil; the eighth stage is signless and effortless, and hence tranquil; being tranquil, it is pure. Alternatively, signless is the eighth stage, tranquil is the ninth stage, and pure refers to the tenth stage; because in the tenth stage, among the two obscurations of afflictions and of the knowable, the habitual propensities and entanglements of the affliction-obscuration are completely exhausted, it is called pure.