Bhagavad Gita · 7.10

बीजं मां सर्वभूतानां विद्धि पार्थ सनातनम्।बुद्धिर्बुद्धिमतामस्मि तेजस्तेजस्विनामहम्॥

bījaṁ māṁ sarva-bhūtānāṁ viddhi pārtha sanātanam buddhir buddhimatām asmi tejas tejasvinām aham

O Partha, know Me to be the eternal seed of all beings. I am the intelligence of the intelligent and the brilliance of the brilliant.

— Bhagavad Gita 7.10

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