Bhagavad Gita 14.6 is Chapter 14, Verse 6, in Gunatraya Vibhaga Yoga (The Three Gunas). Below are the Sanskrit text, a transliteration, a plain-English translation and an explanation.
tatra sattvaṁ nirmalatvāt prakāśakam anāmayam sukha-saṅgena badhnāti jñāna-saṅgena cānagha
"Of these, sattva, being pure, is illuminating and free from disease; it binds by attachment to happiness and attachment to knowledge, O sinless one."
What This Means:
Sattva is the purest guna, it brings clarity, light, and freedom from suffering. But even sattva binds: it creates attachment to happiness and attachment to knowledge. Even good things can become chains.
Going Deeper:
'Nirmalatvāt', due to purity. 'Prakāśakam', illuminating (enables clarity). 'Anāmayam', free from disease/suffering. Sattva seems entirely positive, yet 'sukha-saṅgena badhnāti', it binds through attachment to happiness, and 'jñāna-saṅgena', through attachment to knowledge. The spiritual ego that says 'I am wise, I am peaceful' is sattvic bondage.
How To Apply This:
Beware of spiritual materialism, becoming attached to your spiritual progress, your wisdom, your peacefulness. Even sattvic qualities can become identity and thus bondage. Hold your virtues lightly.
Key Sanskrit Terms: