大般涅槃經義記 3.263

3.263

第二句中，「若說如來是無常者」牒前倒想，「名大罪苦」結以為苦。此是罪過，與苦作因，故名罪苦。

In the second clause, 'if one says that the Tathāgata is impermanent' recapitulates the aforementioned inverted notion; 'is called great sinful suffering' concludes it as suffering. This is a transgression that acts as a cause for suffering, and is therefore called sinful suffering.