妙法蓮華經玄義 1.51

1.51

所以引二文者，古佛事定，舉要略以釋疑。今佛說竟，舉要略以付囑。中間正當機廣說，故不引證耳。若引者，「開、示、悟、入」，即其文也。「為大事因緣故」，證名；「佛之知見」，證體；「開示悟入」，證宗；「為令眾生」，證用；「此異餘經」，證教也。

The reason two passages are adduced is that the affairs of the ancient Buddha were settled, so he cited the essentials in brief to resolve doubts; the present Buddha had finished speaking, so he cited the essentials in brief to confer entrustment. In between, he was expounding at length directly in response to spiritual capacities, which is why proof is not adduced there. If one were to adduce proof [from there], 'opening, displaying, awakening, and entering' is precisely the text: 'for the sake of the one great cause and condition' proves the title; 'the knowledge and vision of the Buddha' proves the substance; 'opening, displaying, awakening, and entering' proves the central purport; 'in order to cause sentient beings' proves the function; and 'this differs from other sūtras' proves the teaching.