SB 3.5.25

sā vā etasya saṁdraṣṭuḥ
 śaktiḥ sad-asad-ātmikā
māyā nāma mahā-bhāga
 yayedaṁ nirmame vibhuḥ
Word for word: 
— that external energy; — is either; etasya — of the Lord; saṁdraṣṭuḥ — of the perfect seer; śaktiḥ — energy; sat-asat-ātmikā — as both the cause and the effect; māyā nāma — called by the name māyā; mahā-bhāga — O fortunate one; yayā — by which; idam — this material world; nirmame — constructed; vibhuḥ — the Almighty.
Translation: 
The Lord is the seer, and the external energy, which is seen, works as both cause and effect in the cosmic manifestation. O greatly fortunate Vidura, this external energy is known as māyā or illusion, and through her agency only is the entire material manifestation made possible.
Purport: 

The material nature, known as māyā, is both the material and efficient cause of the cosmos, but in the background the Lord is the consciousness for all activities. As in the individual body the consciousness is the source of all energies of the body, so the supreme consciousness of the Lord is the source of all energies in material nature. This is confirmed in Bhagavad-gītā (9.10) as follows:

mayādhyakṣeṇa prakṛtiḥ
 sūyate sa-carācaram
hetunānena kaunteya
 jagad viparivartate

“Throughout all the energies of material nature there is the hand of the Supreme Lord as the final superintendent. Due to this supreme cause only, the activities of material nature appear planned and systematic, and all thing regularly evolve.”