Bhagavad Gita Chapter 2, Verse 58

यदा संहरते चायं कूर्मोऽङ्गानीव सर्वशः । इन्द्रियाणीन्द्रियार्थेभ्यस्तस्य प्रज्ञा प्रतिष्ठिता ॥

yadā saṁharate cāyaṁ kūrmo 'ṅgānīva sarvaśaḥ | indriyāṇīndriyārthebhyas tasya prajñā pratiṣṭhitā ||

When one withdraws the senses from sense objects completely, like a tortoise withdrawing its limbs from all sides—their wisdom is established.

Krishna offers a vivid image: like a tortoise withdraws its limbs completely ('sarvaśaḥ'—from all sides) into its shell when threatened, a wise person can withdraw their senses ('indriyāṇi') from sense-objects ('indriya-arthebhyaḥ'). This isn't suppression—it's skillful mastery. The tortoise doesn't argue with danger; it simply withdraws. Then 'prajñā pratiṣṭhitā'—wisdom is established. You can engage your senses when appropriate, withdraw them when needed. That voluntary control is the mark of steady wisdom.