觀無量壽佛經疏 3.17

3.17

Answer: "The sun disk shines constantly, signifying the enduring radiance of Sukhāvatī. Furthermore, fearing that that ground might be uneven, like the heights and depths of this defiled land—yet, as the Sahā world is a dark abode, only the sun can bring light; and in this realm of hills and pits, there are nowhere without heights and depths—if one wishes to take something that can be level, nothing surpasses water. Displaying this mark of what can become level illustrates that lapis lazuli ground."