大般涅槃經義記 7.350

7.350

第三舉淺類深之中，「眾生之性與虛空性俱無實」者，生空是其眾生之性，虛空是前所辯法空，淺深雖殊，俱是本來自體無性，故名為空。

In the third, citing the shallow to illustrate the deep: as for "the nature of sentient beings and the nature of space are both without reality," the emptiness of sentient beings is the nature of sentient beings, and space is the emptiness of dharmas explained earlier; although shallow and deep differ, both are originally, in their intrinsic nature, without self-nature, and are therefore called empty.