妙法蓮華經玄義 8.119

8.119

今約通通論四門者，上三藏四門，皆滅色入空，如析實人頭等六分，求人不得，故名為空。通教四門皆即色是空，如觀鏡像，六分即空，不待析盡為空。《大論》云：「佛告比丘：觀空即疊，觀疊即空。」此是體門異析門也。

Now discussing the four gates with respect to generally connecting to the shared: the four gates of the Tripiṭaka [teaching] above all extinguish form to enter emptiness, like analyzing the six parts—the head and so forth—of an actual person, finding no person to be grasped, and therefore calling it empty. The four gates of the shared teaching are all form itself being empty, like observing an image in a mirror: the six parts are empty right as they are, without waiting for analytical exhaustiveness to become empty. The Da zhidu lun states: 'The Buddha told the monks: Viewing emptiness is viewing cloth; viewing cloth is viewing emptiness.' This is the gate of essential identity being different from the gate of analysis.