法華義疏 9.199

9.199

「是時大樂說」下，第三、次明開塔。所以須開塔者，向雖親承音旨，未若覩形生信，故須開塔現形成信彌篤，則是開方便門示法身真實。就文為二：第一、普集分身為開塔之緣；第二、正明開塔。所以普集分身者，欲辨本一迹多也。所以然者，釋迦與諸佛互指為分身，即知彼此皆非實佛，別有統一之本為妙極法身，故垂淨穢等迹，則知法身不二、迹身不一也。

From "At that time Mahāpratibhāna" downward is the third [major section], next clarifying the opening of the stūpa. As for why it was necessary to open the stūpa: although they had just directly received the verbal message, it was not as effective as beholding his form to give rise to faith. Therefore it was necessary to open the stūpa to manifest his form, making faith ever more firm; this is opening the gate of expedient means to display the real dharmakāya. Regarding the text, there are two parts: first, universally assembling the emanated bodies serves as the condition for opening the stūpa; second, directly clarifying the opening of the stūpa. As for why the emanated bodies were universally assembled: it was to distinguish the fundamental oneness and the trace multiplicity. Why is this so? Śākyamuni and the various Buddhas mutually point to one another as emanated bodies; thus we know that neither is the real Buddha, and that there is separately a unified fundamental source that is the wondrous ultimate dharmakāya, which therefore projects pure and defiled traces. Thus we know that the dharmakāya is non-dual, while the trace bodies are not one.