大般涅槃經集解 55.86

55.86

案僧亮曰：難意不以不善為因故言無，非一切無也，故取六無之中有時無也。

Sengliang comments: The intent of the challenge is that because it does not take unwholesome states as its cause, it is said to have "no cause," not that it is entirely without cause; hence he takes "having a time of non-existence" from among the six kinds of non-existence.