佛說盂蘭盆經疏 2.58

2.58

當為者，能救之心。七世下，所救之境。約境明心，故云勝也。七世者，所生父母，不同儒教取上代祖宗。厄難中者，通於存歿。歿則地獄鬼畜，存則病痛枷禁，皆名厄難。七世父母雖似轉疎，皆是生我修道之器。既蒙鞠育，豈負深恩。故三藏云：「天地覆載，既無憚於劬勞；幽顯沈淪，理合答於罔極。」

"Should, for the sake of" refers to the mind capable of rescuing. From "parents of seven lifetimes" downward is the realm to be rescued. Clarifying the mind in reference to the realm is why it is called "superior." "Seven lifetimes" refers to the parents who gave birth to one, unlike Confucian teaching which takes remote ancestors. "In distress" applies to both the living and the dead: the dead in the hells, hungry ghosts, and animals; the living in illness, pain, cangues, and imprisonment—all are called "distress." Although the parents of seven lifetimes seem progressively more distant, all of them gave birth to me as a vessel for cultivating the path. Having received their nurture, how could one turn one's back on such deep kindness? Thus the Tripiṭaka Master says: "Heaven and earth cover and support, shrinking from no toil; sinking in the unseen or manifest, reason demands repaying the boundlessness [of their kindness]."