俱舍論記 11.94

11.94

「於下處生至要作下地化」者，此即第二明下天昇上。下天昇見上，總由三緣：一自得通能往、二依他得通者往、三上天接往。若上天來下，或下天至上，下見上天。然下地下界眼不能見上地上界色，非其境界故，以上色細故。如下地身不覺上觸，故上來下非自身來，要作下地化方下得見，若自身來下眼不見。

"Being born in a lower abode... must create an apparition of the lower stage": this is the second, explaining the ascent of lower devas to the higher ones. A lower deva ascending to see a higher one occurs through three conditions in total: first, having obtained supernormal powers oneself and being able to go; second, relying on another who has obtained supernormal powers to go; third, being received and taken up by a higher deva. When a higher deva comes down, or a lower deva goes up, the lower deva sees the higher deva. However, the eye of a lower stage and lower realm cannot see the visible forms of a higher stage and higher realm, because it is not its perceptual object, since higher forms are subtle. Just as a body of a lower stage does not perceive a higher tangible, when an upper deva comes down, he does not come in his own body; he must create an apparition of the lower stage before he can be seen by the lower deva; if he came in his own body, the eye of the lower deva would not see him.