Śrīmad-Bhāgavatam · Text 7.1.10
Who is speaking and story frame
यदा सिसृक्षु: पुर आत्मन: परो
रज: सृजत्येष पृथक् स्वमायया ।
सत्त्वं विचित्रासु रिरंसुरीश्वर:
शयिष्यमाणस्तम ईरयत्यसौ ॥ १० ॥
yadā sisṛkṣuḥ pura ātmanaḥ paro
rajaḥ sṛjaty eṣa pṛthak sva-māyayā
sattvaṁ vicitrāsu riraṁsur īśvaraḥ
śayiṣyamāṇas tama īrayaty asau
When the Supreme Personality of Godhead creates different types of bodies, offering a particular body to each living entity according to his character and fruitive actions, the Lord revives all the qualities of material nature — sattva-guṇa, rajo-guṇa and tamo-guṇa. Then, as the Supersoul, He enters each body and influences the qualities of creation, maintenance and annihilation, using sattva-guṇa for maintenance, rajo-guṇa for creation and tamo-guṇa for annihilation.
Read Śrīla Prabhupāda's purport on Vedabase.io