法苑珠林 3.43

3.43

問曰。若無象馬四足眾生。彼天欲游何所乘耶。答曰。即如論說。還自釋言。雖無象馬諸天欲出。以福力故。即有象馬。隨心化起。任意所乘乘竟化滅。此教放逸鳥等遍在六天皆悉有之。常與諸天為師訶責放逸。不唯焰摩已上偏獨有也。

Question: If there are no four-footed creatures like elephants and horses, what do those devas ride when they wish to roam? Answer: As the treatise itself explains: Although there are no elephants or horses, when the devas wish to go forth, by the power of their merit, elephants and horses are manifested according to their thoughts; they ride them as they please, and once the riding is finished, they vanish. These birds that admonish negligence and others are universally present throughout all six heavens; they always act as teachers to the devas, rebuking negligence, and are not solely present above Yāma.