四明十義書 1.137

1.137

又彼方等歷事作觀，加行進功，故云心心相續觀道無間，方得入不二法門。

Furthermore, in that Vaipulya, one performs contemplation while traversing phenomena, applying expedients and advancing effort; hence it says that 'thought after thought succeeds each other, and the path of contemplation is without interruption' before one can enter the non-dual Dharma gate.