Guṇa-Traya-Vibhāga Yoga · Verse 5
सत्त्वं रजस्तम इति गुणाः प्रकृतिसम्भवाः | निबध्नन्ति महाबाहो देहे देहिनमव्ययम्
sattvaṃ rajas tama iti guṇāḥ prakṛti-sambhavāḥ | nibadhnanti mahā-bāho dehe dehinam avyayam
Luminosity, activity and inertia — these qualities born of nature — bind the embodied self, O mighty-armed!, to the body.
The three guṇas — strands of nature — constitute the fabric of prakṛti. They are not merely qualities but substantive principles that constitute all phenomena.
Sattva (illumination), rajas (activity), and tamas (inertia) are the three phases of all natural process: conservation, transformation, and dissolution.
They nibadhnanti — bind — the dehin — embodied one — through identification. The avyaya — indestructible — Self becomes entangled in the changing field.