According to great sages, that which is the basis of the three modes of material nature and which manifests the variegated universe is called the sūtra or mahat-tattva. Indeed, this universe is resting within that mahat-tattva, and due to its potency the living entity undergoes material existence.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
तामाहुस्त्रिगुणव्यक्तिं सृजन्तीं विश्वतोमुखम् । यस्मिन् प्रोतमिदं विश्वं येन संसरते पुमान्
tāmāhustriguṇavyaktiṃ sṛjantīṃ viśvatomukham | yasmin protamidaṃ viśvaṃ yena saṃsarate pumān
SB 11.9.20