俱舍論記 3.62

3.62

「若如是者至誰之異熟」者，問。若唯異熟，阿羅漢留命或經百年或千年等，皆由現在布施衣等引壽續前，應非異熟。如是命根，誰之異熟，而言唯命定異熟。

Regarding "If so […] whose vipāka is it?": this is a question. If it is solely vipāka, when an arhat prolongs life, whether for a hundred years or a thousand years, it is entirely because of present-moment giving of robes and so forth drawing forth lifespan to continue what preceded; it should not be vipāka. As for such a life faculty, whose vipāka is it, that you say only the life faculty is definitively vipāka?