From https://cbetaonline.dila.edu.tw/zh/X1464

蓋聞虗而有鳴荅之聲。
寂而無形影之相。
然谷響自然。
非呼之而不答。
佛身無作。
非扣之而不彰。

“It is said: in emptiness, there is both the sound of a call and response; in stillness, there is no appearance of form or shadow. A valley naturally has an echo, but without a call there is no response. The Buddha’s body does not stir; without a request there is no manifestation.”

Master Zhongfeng’s “Steadfast Mindfulness in Three Periods”
https://ibpsottawa.org/wp-content/uploads/2021/08/FGS_LiturgyofSteadfastMindfulnessinThreePeriods.pdf