瑜伽師地論略纂 11.125

11.125

論解難行靜慮中，有三難行。第一難行者，謂菩薩已得引發神通，極善成就靜慮，應生上界，為利有情故還生欲界，是為難行。此中意也。

In the treatise's explanation of dhyāna difficult to practice, there are three difficult practices. As for the first difficult practice, it means that a bodhisattva, having already attained the evocation of supernormal powers and having extremely well accomplished dhyāna, ought to be born in the higher realms, yet for the sake of benefiting sentient beings is reborn in the desire realm—this is difficult practice. This is the meaning here.