金光明經文句記 3.198

3.198

初、「鼓是」下，明似智會法起用。上鼓表三光三佛，三秖是一三。今對信相機智所觀，合三為一，但名法身。婆羅門表真似淨行，既是隣真，故經稱似。圓似能伏同體惑染，故名淨智。以此淨智會本常理，乃以甘露相似相應。能以妙音遍三千界、滅苦生樂，故使經文復以擊鼓表似位三身。若不爾者，則信相本性與佛天殊，佛之應用非信相感也。行者應了釋迦、信相同興此夢，故有懺法利益眾生耳。

First, from "The drum is..." onward, clarifies that approximate wisdom accords with the principle and initiates function. Above, the drum signified the three lights and three Buddhas, and the three are merely a single three. Now, with respect to the capacity and wisdom contemplated by Ruciraketu, the three are combined into one, which is named solely the Dharma body. The brāhmaṇa signifies pure practice that is true or approximate; since it is adjacent to truth, the commentary calls it approximate. Perfect approximate [wisdom] is able to subdue the defilements identical in essence, and is therefore called pure wisdom. Using this pure wisdom to accord with the fundamental eternal principle, one accords approximately through ambrosia (amṛta). Because he is able through wonderful sounds to pervade the three thousand realms, extinguish suffering, and produce bliss, the sūtra text also uses the striking of the drum to symbolize the three bodies of the stage of approximate [enlightenment]. Were it not so, then Ruciraketu's original nature would be entirely different from the Buddha's, and the Buddha's responsive function would not be evoked by Ruciraketu. Practitioners should understand that Śākyamuni and Ruciraketu together gave rise to this dream, which is why there is the rite of repentance to benefit sentient beings.