維摩經略疏 2.9

2.9

問：何故從餘四天下來？答：上界處空，來處難知。以下擬上，故言從餘四天下來也。

Question: Why did they come from other four-continent worlds? Answer: The higher realms abide in space, so the place they came from is difficult to know. By using the lower to analogize the upper, it says they came from other four-continent worlds.