摩訶止觀 2.107

2.107

其師過者，不達根性，不解佛意。佛說「貪欲即是道」者，佛見機宜，知一種眾生底下薄福，決不能於善中修道。若任其罪，流轉無已；令於貪欲修習止觀，極不得止，故作此說。譬如父母見子得病，不宜餘藥，須黃龍湯，鑿齒瀉之，服已病愈。佛亦如是，說當其機。快馬見鞭影，即到正路。貪欲即是道，佛意如此。若有眾生不宜於惡修止觀者，佛說諸善名之為道。佛具二說，汝今云何呵善就惡？若其然者，汝則勝佛。公於佛前灼然違反。

As for the error of their masters: they fail to comprehend faculties and dispositions, and do not understand the Buddha's intent. When the Buddha taught that "greed and desire are themselves the Way," the Buddha perceived what was suitable to their capacities, knowing that there is a class of sentient beings of base and meager merit who are utterly incapable of cultivating the Way in the midst of wholesome [states]. If left to their offenses, their transmigration would have no end; so he had them cultivate calming and contemplation in the midst of greed and desire as an absolute last resort, which is why he spoke in this way. It is like parents seeing their child afflicted with an illness for which no other medicine is suitable, requiring 'Yellow Dragon Decoction' (huanglong tang), prying open the teeth to purge it, after taking which the illness is cured. The Buddha is also like this, teaching in accordance with their capacity. A swift horse, merely seeing the shadow of the whip, immediately takes the correct path. 'Greed and desire are themselves the Way'—such was the Buddha's intent. If there were sentient beings for whom it was not suitable to cultivate calming and contemplation in the midst of unwholesome [states], the Buddha taught various wholesome [states] and named them 'the Way.' The Buddha possessed both teachings. How can you now disparage the wholesome and run to the unwholesome? If that were so, you would surpass the Buddha, openly and glaringly contradicting him to his face.