法華義疏 9.215

9.215

若一變者時眾則不覺土曠佛多，今欲顯土曠佛多令起信敬，故三變也。二、欲表三根之穢而得淨悟也。又表三乘之穢皆除、顯一乘之淨如淨土也。又表彼此無量土同為一佛土、彼此無量身同一法身也。

If it were transformed only once, the assembly at that time would not perceive that the land was vast and the Buddhas were many. Now, wishing to reveal that the land is vast and the Buddhas are many so as to cause them to generate faith and reverence, it was transformed three times. Second, it is intended to represent that the defilement of the three faculties attains pure awakening. Furthermore, it represents that the defilements of the three vehicles are all removed, revealing the purity of the ekayāna just like a pure land. Furthermore, it represents that the mutually immeasurable lands are together one Buddha-land, and the mutually immeasurable bodies are together one dharmakāya.