成唯識論述記 3.596

3.596

述曰：此言顯上相續之義，此義可知。言性堅者，四義受熏即初堅義，乃至金剛此不斷故，故能受熏。若不堅者，如六、七識應不受熏。復言持種令不失者，簡經部等色、心受熏而能持種，於無色界入無心時此種便失，此識不爾，種不失故，故不可斷。此解恒義。

The Commentary states: These words reveal the meaning of "continuous" above; this meaning can be understood. "Its nature is firm" refers to the first, "firmness," among the four criteria for receiving perfuming: up to the vajra[-like samādhi] this [consciousness] is uninterrupted, and therefore capable of receiving perfuming. If it were not firm, then like the sixth and seventh consciousnesses, it would not receive perfuming. Furthermore, saying that it "holds seeds and causes them not to be lost" excludes the Sautrāntikas and others who hold that rūpa and citta receive perfuming and are able to sustain seeds: upon entering mindlessness in the immaterial realm, these seeds would be lost. This consciousness is not like that, because its seeds are not lost; therefore it cannot be discontinuous. This explains the meaning of "constantly."