摩訶止觀 2.43

2.43

觀陰既爾，十二因緣如谷響，如芭蕉堅、露、電等，一時運念，令空觀成，勤須修習，使得相應。觀慧之本，不可闕也。

Contemplating the aggregates being thus, the twelve links of conditioned arising are like an echo in a valley, like the solidity of a plantain, like dew, lightning, and so forth. Bringing mindfulness to bear all at once, bring the contemplation of emptiness to completion, diligently cultivating and practicing it so that correspondence is attained. This is the root of contemplative wisdom and must not be omitted.