妙法蓮華經玄贊 8.427

8.427

贊曰：下答。有二：初陳多寶本願，後召化佛。此初也。彼佛說經塔涌為證，塔開佛現化佛為證。又我塔開，假分身以邀重；我今證說，明此經而可信故。願彼佛分身佛集方可塔開。

The Commentary says: Below is the response. It has two parts: first, setting forth Prabhūtaratna's original vow; later, summoning the transformation buddhas. This is the first. For that buddha's preaching of the sūtra, the springing up of the stūpa serves as witness; for the opening of the stūpa and the buddha's manifestation, the transformation buddhas serve as witness. Furthermore, for my stūpa to open, it relies on the emanation bodies to invite veneration; I now bear witness to the preaching, making clear that this sūtra is to be trusted. Therefore, he vowed that only when that buddha's emanation buddhas have assembled may the stūpa be opened.