註華嚴經題法界觀門頌 2.89

2.89

驀地喚一聲，猶如鏡中現。此頌空谷者，事法體空因也。外叫者，疎助緣也。顯喻因緣無性，是事家用也。

Suddenly letting out a shout, / It appears just like in a mirror. In this verse, the "empty valley" is the cause: phenomenal dharmas being empty in substance. The "call from outside" is the distant auxiliary condition. Revealing by metaphor that causes and conditions have no nature is the function of the phenomenal school.