妙法蓮華經玄贊 4.8

4.8

四二運用廣體，唯以因智名為一乘，火宅喻中與諸菩薩及聲聞眾乘此寶乘直至道場，唯因行故。

Fourth is the essence of broad conveyance and functioning: Only causal wisdom is named the Single Vehicle. In the parable of the burning house, riding this jewel carriage straight to the place of awakening together with the bodhisattvas and the assembly of śrāvakas is solely on account of causal practice.