摩訶止觀 3.228

3.228

是故如來巧用悉檀，興廢適時，順機而作，皆益眾生。是故如來不空說法，為度人故，應興、應廢也。對三權說一實，實存權廢，已如前說。

Therefore the Tathāgata skillfully employs the siddhāntas, instituting and abolishing at the appropriate times, acting in accordance with capacities, all to benefit sentient beings. For this reason the Tathāgata does not expound the Dharma in vain; because it is for delivering people, it ought to be instituted and ought to be abolished. Expounding the one real in contrast to the three provisionals, where the real remains and the provisionals are abolished, has already been explained above.