Bhagavad Gita Chapter 14, Verse 6

तत्र सत्त्वं निर्मलत्वात्प्रकाशकमनामयम् | सुखसङ्गेन बध्नाति ज्ञानसङ्गेन चानघ ||

tatra sattvaṁ nirmalatvāt prakāśakam anāmayam sukha-saṅgena badhnāti jñāna-saṅgena cānagha

O sinless one, among them, sattva, being pure, is illuminating and healthy. It binds through attachment to happiness and through attachment to knowledge.

Krishna describes sattva guna: 'Tatra sattvaṁ'—among them, sattva. 'Nirmalatvāt prakāśakam anāmayam'—being pure, it is illuminating (prakāśakam) and healthy (anāmayam). Sattva brings clarity, peace, and understanding. But here's the key: 'Sukha-saṅgena badhnāti jñāna-saṅgena ca'—it binds (badhnāti) through attachment to happiness (sukha-saṅgena) and through attachment to knowledge (jñāna-saṅgena). This is crucial: even the 'good' mode binds you. Sattva is the purest mode, but it still binds you through attachment. When you're attached to the happiness that sattva brings, or attached to the knowledge and clarity it provides, you're still bound. You're still in material existence, just in a more refined form. Understanding this helps you see that even sattva needs to be transcended for true freedom.