佛說盂蘭盆經疏 2.33

2.33

A child in urgent need appeals to the father; a minister in urgent need appeals to the lord. When one's own power is insufficient, it is right to turn to the Buddha. The disciple had diligently contemplated the four truths and already realized the three knowledges, capable of overturning mountains and rivers and revolving the sun and moon. How could he have anticipated that his mother would be entangled in ultimate suffering, her life as if hung upside down, and that exhausting his filial sincerity and using all his supernormal transformations would nevertheless fail to eliminate her evil retribution and temporarily relieve her starving belly? This is why he rushed back crying and weeping, fully expressing his mournful plea.