金剛經纂要刊定記 5.30

5.30

報佛下。正明所喻。謂進修多劫福智圓明，純淨無垢更無過此，故云無上。獨王（去聲）法界故號法王。大有二義：一約體，身智郭周故。二約位，諸聖莫及故。

"The reward buddha, etc.": this directly clarifies the tenor of the metaphor. It means that through cultivating and advancing across many kalpas, merit and wisdom are completely fulfilled and luminous; being purely clean and undefiled, nothing further surpasses this, hence it is said to be "unsurpassed." Uniquely reigning over the dharmadhātu, he is therefore styled the Dharma King. "Great" has two meanings: first, in terms of essence, because his body and wisdom encompass all; second, in terms of rank, because none of the nobles can match him.