Bhagavad Gita Chapter 2 Verse 58

yadā saṃharate cāyaṃ kūrmo’ṅgānīva sarvaśaḥ
indriyāṇīndriyārthebhyastasya prajñā pratiṣṭhitā

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

yadā = when; saṃharate = winds up; ca = also; ayaṃ = he; kūrmaḥ = tortoise; aṅgāni = limbs; iva = like; sarvaśaḥ = altogether; indriyāṇi = senses; indriyārthebhyaḥ = from the sense objects; tasya = his; prajñā = consciousness; pratiṣṭhitā = fixed.;