首楞嚴義疏注經 9.112

9.112

四空天人容是業報，彼四天王即是權化。以入大乘首楞嚴定，為欲遊戲四禪、四空諸禪三昧成佛事故。

The heavenly beings of the four formless [heavens] are merely karmic retributions, whereas those four heavenly kings are provisional manifestations. This is because they have entered the Mahāyāna Śūraṅgama samādhi, desiring to sport in the various dhyāna-samādhis of the four dhyānas and four formless [attainments] in order to accomplish Buddha-activities.