淨名經集解關中疏 1.166

1.166

所以者何。菩薩隨所化眾生而取佛土　此二明列釋四句文四。此初明佛國寬狹不同所以。肇曰。此下釋所以眾生即佛土也。佛土者即眾生之影響耳。夫形修影長形短影促。日月使之然乎。形自然耳。故隨所化眾生之多少而取佛土之寬狹也。是以佛土或以四天下。或以三千。或以恒沙為一國也。

"Why is this? A bodhisattva acquires a buddha-land according to the sentient beings he transforms." This second clarifies the sequential explanation of the four clauses, which has four parts. This first explains the reason for the different expansiveness or narrowness of buddha-lands. Sengzhao says: "Below this, it explains why sentient beings are themselves the buddha-land. The buddha-land is simply the shadow and echo of sentient beings. When a form is tall, its shadow is long; when a form is short, its shadow is brief. Do the sun and moon make it so? It is simply the nature of the form itself. Therefore, according to the greater or lesser number of sentient beings transformed, he acquires a buddha-land of greater or lesser extent. Hence, a buddha-land may take the four continents, a trichiliocosm, or sands of the Ganges as one realm."