大般涅槃經義記 2.5

2.5

自下第二對上所請許說違住。「亦當為汝先說甘露」是許說也，對前許答，故云亦當。望後取滅，名為先說；然後涅槃，違其請住。向前比丘第五請中云言「示我甘露正道」，故許為說；復言「久住勿入涅槃」，故今違之。

Below is the second [part], in response to what was requested above, promising to preach while refusing to abide. "I shall also first explain ambrosia for your sake" is the promise to preach; in contrast to the earlier promise to answer, it therefore says "shall also." Looking forward to entering extinction, it is called "first explain"; and thereafter entering nirvāṇa refuses their request to abide. Earlier, in the fifth request of the bhikṣus, it was said: "Show us the correct path of ambrosia," and therefore he promises to preach it for them; it was also said: "Abide long and do not enter nirvāṇa," and therefore he now refuses this.