Bhagavad Gita 13.12

Constant yearning for the knowledge of the Self, and pondering over the lessons of the great Truth—this is wisdom; all else is ignorance.

अध्यात्मज्ञाननित्यत्वं तत्त्वज्ञानार्थदर्शनम्।एतज्ज्ञानमिति प्रोक्तमज्ञानं यदतोन्यथा॥

adhyātmajñānanityatvaṃ tattvajñānārthadarśanam|etajjñānamiti proktamajñānaṃ yadatonyathā||

English translation (above): Shri Purohit Swami (1935), public domain. Sanskrit text via github.com/gita/gita (Unlicense).