Chapter 2 · verse 58 · gita.yoga.org

Bhagavad Gita 2.58

यदा संहरते चायं कूर्मोऽङ्गानीव सर्वशः। इन्द्रियाणीन्द्रियार्थेभ्यस्तस्य प्रज्ञा प्रतिष्ठिता

When, like the tortoise which withdraws all its limbs on all sides, he withdraws his senses from the sense-objects, then his wisdom becomes steady.