大般涅槃經集解 15.23

15.23

案僧宗曰：客塵者，以三界外惑為舊，三界內惑為客，以根本為義也。如前品說燈燼，譬後明不還義也。

Sengzong notes: Regarding 'adventitious defilements', the delusions outside the three realms are considered old, while the delusions within the three realms are considered adventitious, taken in the sense of the fundamental. As in the preceding chapter's explanation of the lamp's embers, it subsequently illustrates the meaning of non-returning.