Verse 5

तिष्ठत्येतास्ववस्थासु भेदतः कल्प्यते त्रिधा ।सत्त्वं रजस्तम इति एषैव प्रकृतिः स्मृता

In plain words

She stands in these states, and by their difference she is conceived as threefold: sattva, rajas, tamas -- this very one is known as prakṛti.