大般涅槃經義記 2.195

2.195

釋第五中，文別有二：一解前喻明非無常。「星流」舉偈，「謂煩惱」者被破煩惱，「散已滅」等牒舉偈文。謂諸如來煩惱滅已，合散已滅；不在五趣，合向偈中莫知所在；二「是故」下結成常義。是佛惑滅，不在五趣，故得為常。

In explaining the fifth, the text has two distinct parts: First, it explains the previous metaphor to clarify that it is not impermanent. 'Sparks scattering' cites the verse; 'meaning afflictions' refers to the afflictions being shattered; 'extinguishing once scattered,' etc., repeats and cites the text of the verse. It means that once the afflictions of all Tathāgatas are extinguished, this matches 'extinguishing once scattered'; their not being in the five destinies matches 'none knows where they are' in the verse just quoted. Second, from 'therefore...' onward concludes the meaning of permanence. Because the Buddha's delusions are extinguished and he is not in the five destinies, he is therefore permanent.