妙法蓮華經玄義 7.62

7.62

三、本國土者，本既成果，必有依國。今既迹在同居、或在三土，中間亦有四土，本佛亦應有土，復居何處？文云：「自從是來，我常在此娑婆世界說法教化。」按此文者，實非今日迹中娑婆，亦非中間權迹處所，乃是本之娑婆，即本土妙也。

Third, the original land: since the original source realized the fruition, it must have a reliant land. Now since the traces reside in the land of shared residence or in the three lands, and the intermediate time also has four lands, the original buddha must also have a land; where then does he dwell? The text says: "Ever since then, I have constantly been in this Sahā world, preaching the Dharma and transforming sentient beings." According to this passage, it is truly not the Sahā of the traces today, nor the place of the provisional traces in the intermediate time, but the Sahā of the original source, which is the subtlety of the original land.