首楞嚴義疏注經 6.80

6.80

人身難得，見佛受化。非天之著樂，餘之多苦，故樂修也。有形有色蘊，如下休咎精明等。無形無色蘊，如下空散消沈等。有想有四蘊，如下鬼神精靈等。無想無四蘊，即下精神化為土木金石等。此上皆非人也。斯則形想雜類，蠢物皆沾，必一其身，乘機即化。

A human body is difficult to obtain, enabling one to see the Buddha and receive transformation. Unlike the attachment to pleasure of devas, or the preponderance of suffering among the rest, they therefore delight in cultivating it. 'Having form' means having the skandha of form, like the auspicious and ominous luminaries below. 'Formless' means lacking the skandha of form, like the empty, dispersed, sunken, and vanished below. 'With thought' means having four skandhas, like ghosts, spirits, essences, and souls below. 'Thoughtless' means lacking four skandhas, namely those whose spiritual essence transforms into earth, wood, metal, and stone below. All the above are non-humans. Thus, diverse classes of form and thought, all wriggling creatures, receive benefit; [the Bodhisattva] necessarily matches their bodies, transforming them on the spur of the moment.