法華義疏 11.168

11.168

有三因緣：一者、時眾聞佛慇懃付囑則重法情深各欲宣持。二、付諸菩薩即令其自行化他。三者、眾生於菩薩有重緣，故令其弘法化物。

There are three causes and conditions: First, when the assembly of that time hears the Buddha earnestly entrust it, their feeling of venerating the Dharma is profound, and each desires to proclaim and uphold it. Second, entrusting it to the bodhisattvas causes them to practice it themselves and convert others. Third, sentient beings have profound karmic affinity with the bodhisattvas, hence he causes them to propagate the Dharma and convert beings.