大毘盧遮那成佛經疏 10.39

10.39

猶善能行此利益有情之行，真是佛子，從善性而生，故名善子。從佛而生，故名佛子也。此菩薩即能說種種三乘行門利益眾生，如《十輪》廣說。次文殊入佛加持神力三昧，此加持三昧如上《毘盧經》初說也。

Being able to skillfully practice this practice of benefiting sentient beings, he is truly a Buddha-son, born from the good nature, and therefore called 'good son'. Being born from the Buddha, he is called a 'Buddha-son'. This bodhisattva can expound various practice gateways of the three vehicles to benefit sentient beings, as broadly explained in the Daśacakra. Next, Mañjuśrī enters the Samādhi of the Buddha's Empowered Supernatural Power; this adhiṣṭhāna-samādhi is as explained at the beginning of the Mahāvairocana Sūtra above.