CC Madhya 20.301

brahmā, viṣṇu, śiva, — tina guṇa avatāra
tri-guṇa aṅgīkari’ kare sṛṣṭy-ādi-vyavahāra
Word for word: 
brahmā, viṣṇu, śiva — Lord Brahmā, Lord Viṣṇu and Lord Śiva; tina — three; guṇa avatāra — the incarnations of the material qualities; tri-guṇa — the three qualities of material nature; aṅgīkari’ — accepting; kare — does; sṛṣṭi-ādi-vyavahāra — transactions in reference to the creation, maintenance and dissolution.
Translation: 
“There are three functions within this material world. Everything here is created, everything is maintained for some time, and everything is finally dissolved. The Lord therefore incarnates Himself as the controllers of the three qualities — sattva-guṇa, rajo-guṇa and tamo-guṇa [goodness, passion and ignorance]. Thus the transactions of the material world take place.