Bhagavad Gita
2.58

यदा संहरते चायं कूर्मोऽङ्गानीव सर्वशः | इन्द्रियाणीन्द्रियार्थेभ्यस्तस्य प्रज्ञा प्रतिष्ठिता ||५८||

yadā saṁharate chāyaṁ kūrmo'ṅgānīva sarvaśhaḥ indriyāṇīndriyārthebhyas tasya prajñā pratiṣhṭhitā

Translation

One who is able to withdraw his senses from sense objects, as a tortoise draws its limbs within the shell, is firmly fixed in perfect consciousness.

Interpretation

The tortoise metaphor for sense-withdrawal (pratyahara): just as a tortoise pulls all its limbs into its shell when threatened, the wise person can withdraw the senses from their objects at will. This is not the forced suppression of desires but the natural withdrawal that comes when the Self has been found to be more satisfying than any sensory experience.