Vasubandhu's Commentary on the Lotus Sutra, p 107-108Now why did the Buddha, the Blessed One, manifest this miraculous sign? He did so to explain the great Dharma; he manifested a great sign to explain the reason; he manifested a great sign to teach the Lotus Sutra. The Tathāgata manifested a great marvel in order to explain the words and passages of the incomprehensible meaning of the true Dharma (saddharma) that he had attained.
There are two explanations [for why the great assembly] esteemed and relied on Mañjuśrī. What are these two? 1) Because [Mañjuśrī] had [previously] witnessed these states (dharmas), and 2) because he was removed from the causes and conditions [that affected the great assembly] and had accomplished these states (dharmas) within his mind.
A variety of marvels were revealed in order to show various events. It should be well known that the marks of the events were [the marks of] origination, decay, subsistence, and impermanence. Since Mañjuśrī was able to recall these events, and since he had accomplished his task and the cause and the result were complete, he witnessed these states (dharmas).
There are two tasks that he had accomplished: 1) the accomplishment of merits and 2) the accomplishment of wisdom. “That the cause was complete” means he had accomplished omniscience. There is also another type of cause referred to as the condition. “That the condition was complete” means that the various signs had occurred. “That the result was complete” means that Mañjuśrī would explain the true Dharma (saddharma) [to the assembly]. It should be known that various different buddha lands were revealed in order to show the various differences and distinctions in those lands. “Pure land” means the dwelling place of living beings that have no defilements. Just as it says in the Lotus Sutra,
[The Buddha’s ray of light] illuminated all the eighteen thousand worlds in the east . . . and rendered visible the splendor of all those buddha worlds.
“The tathāgatas were foremost” since all the bodhisattvas and others take refuge in them, and since the tathāgatas are the ones who have attained self-mastery among those in the great assemblies of the [buddha] lands, just as it says in the Lotus Sutra, “And all the buddhas abiding in those lands were seen…”