觀無量壽佛經疏 3.16

3.16

問曰：「前教觀日，為知業相等，故令觀日。今此觀中，又教觀水。有何所以？」

Question: "Previously [the sūtra] taught contemplating the sun; it instructed contemplation of the sun in order to know karmic marks and so forth. Now in this contemplation, it again teaches contemplating water. What is the reason for this?"