法華論疏 3.246

3.246

以行菩薩行故，菩薩行便增長，故言增長力無上。故說商主譬喻者，商主即是〈化城品〉導師也。經取能道眾人，故以導師為譬。論取能令價客獲於珍寶，故以商主為譬。

Because one practices bodhisattva practice, the bodhisattva practice then grows; therefore, it is called the peerless power of growth. As for "speaks the merchant leader parable," the merchant leader is the guide of the chapter on the Apparitional City. The sūtra takes the ability to guide the multitude, hence using the guide as a parable; the treatise takes the ability to cause merchants to obtain precious gems, hence using the merchant leader as a parable.