六妙法門 1.19

1.19

復次，觀眾生空，故名為觀；觀實法空，故名為還；觀平等空，故名為淨。復次，空三昧相應，故名為觀；無相三昧相應，故名為還；無作三昧相應，故名為淨。復次，一切外觀名為觀；一切內觀名為還；一切非內非外觀名為淨。故先尼梵志言：「非內觀故，得是智惠；非外觀故，得是智惠；非內外觀故，得是智惠；亦不無觀故，得是智惠也。」

Furthermore, contemplating the emptiness of sentient beings is therefore called contemplation; contemplating the emptiness of real dharmas is therefore called turning back; contemplating equal emptiness is therefore called purification. Furthermore, corresponding with the emptiness samādhi is therefore called contemplation; corresponding with the signless samādhi is therefore called turning back; corresponding with the wishless samādhi is therefore called purification. Furthermore, all external contemplation is called contemplation; all internal contemplation is called turning back; all contemplation that is neither internal nor external is called purification. Therefore, the wanderer Śreṇika said: 'It is not because of internal contemplation that this wisdom is attained; it is not because of external contemplation that this wisdom is attained; it is not because of internal and external contemplation that this wisdom is attained; nor is it because of absence of contemplation that this wisdom is attained.'