妙法蓮華經玄贊 10.267

10.267

解妨者，何故須召妙音以為此品？答：藥王此方苦行自勸眾生，未有他土上人他方勸說，故召妙音遠方行法勸他苦行，故須召之。

Regarding resolving difficulties: why was it necessary to summon Gadgadasvara to constitute this chapter? Answer: Bhaiṣajyarāja practiced austerities in this realm to exhort sentient beings of his own accord, but there was not yet a superior person from another land giving exhortations and expositions from another direction. Therefore Gadgadasvara was summoned from a distant land to practice the Dharma and exhort others to austerities; thus it was necessary to summon him.