Bhagavad Gita · 14.11

सर्वद्वारेषु देहेऽस्मिन्प्रकाश उपजायते।ज्ञानं यदा तदा विद्याद्विवृद्धं सत्त्वमित्युत॥

sarva-dvāreṣhu dehe 'smin prakāśha upajāyate jñānaṁ yadā tadā vidyād vivṛddhaṁ sattvam ity uta

When the light of knowledge shines through all the gates of the body, then it should be understood that sattva has become predominant.

— Bhagavad Gita 14.11

Source: Sacred-Texts.com (Sanskrit) + Bhagavad-Gita.io (translations)