瑜伽師地論略纂 5.74

5.74

總釋空差別中，有兩番釋：初依無學者四種空性、後陳有學者四空差別。然四空中，初「所觀察空」正是觀境，後之三種空成滿位，因空所除，假名為空。由觀察空，空無所執，後三不爾，故假名空。　「彼果空」者，謂空滿位，由觀空故，煩惱皆滅。　「內空」者，由觀空故，內計執滅。　「外空」者，由觀空故，空無欲愛。

Within the general explanation of the distinctions of emptiness, there are two sets of explanations: first, relying on the four kinds of emptiness of those beyond study; second, stating the distinctions of the four kinds of emptiness of those in training. However, among the four kinds of emptiness, the first, "emptiness as the observed," is precisely the object of observation; the latter three are the stage of the completion of emptiness, which are metaphorically named "emptiness" because they are what is eliminated by emptiness. Due to the emptiness of observation, the imagined is empty and non-existent; the latter three are not like this, and are therefore metaphorically named emptiness. "The emptiness that is its fruit" refers to the stage of the completion of emptiness: because of observing emptiness, afflictions are all extinguished. "Internal emptiness" means: because of observing emptiness, internal conceptual grasps are extinguished. "External emptiness" means: because of observing emptiness, one is empty of desire and craving.