瑜伽論記 20.157

20.157

或由生故者，有釋：欲菩薩自生天故，能自在施，或可觀他勝生故行慧施。今解：由生剎利等勝生故令行慧施。

As for "or due to birth": another explanation says that because the desiring bodhisattva is born in the heavens himself, he is able to give freely; or it may mean practicing wise giving through observing others' superior births. The present explanation is: causing them to practice wise giving because of being born into superior births such as kṣatriya.