Bhagavad Gita 2.58

yadā saḿharate cāyaḿ
kūrmo ‘ńgānīva sarvaśaḥ
indriyāṇīndriyārthebhyas
tasya prajñā pratiṣṭhitā

Translation of Bhagavad Gita 2.58

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

Commentary by Sri A.C. Bhaktivedanta Swami Prabhupada of Gaudiya Sampradaya:

The test of a yogi, devotee, or self-realized soul is that he is able to control the senses according to his plan. Most people, however, are servants of the senses and are thus directed by the dictation of the senses. That is the answer to the question as to how the yogi is situated. The senses are compared to venomous serpents. They want to act very loosely and without restriction. The yogi, or the devotee, must be very strong to control the serpents—like a snake charmer. He never allows them to act independently. There are many injunctions in the revealed scriptures; some of them are do-not’s, and some of them are do’s. Unless one is able to follow the do’s and the do-not’s, restricting oneself from sense enjoyment, it is not possible to be firmly fixed in Krishna consciousness. The best example, set herein, is the tortoise. The tortoise can at any moment wind up his senses and exhibit them again at any time for particular purposes. Similarly, the senses of the Krishna conscious persons are used only for some particular purpose in the service of the Lord and are withdrawn otherwise. Arjuna is being taught here to use his senses for the service of the Lord, instead of for his own satisfaction. Keeping the senses always in the service of the Lord is the example set by the analogy of the tortoise, who keeps the senses within.

Commentary by Sri Vishvanatha Chakravarthi Thakur of Gaudiya Sampradaya:

This verse answers the question, “How does he sit?” (kim asita)

He withdraws his senses such as the ear from the objects of the senses such as sound. Stopping the movement of the independent senses towards the external objects, he establishes them without movement within. This is the “sitting” of the person situated in prajna. An example is given. He does so, just as the turtle fixes his senses such as mouth and eyes within himself by his will.

Commentary by Sri Ramanuja of Sri Sampradaya:

2.58 And besides, yada, when; ayam, this one, the sannyasin practising steadfastness in Knowledge; samharate, fully withdraws; [‘Fully’ suggests absolute firmness in withdrawal, and ‘withdraws’ suggests full control over the organs] indriyani, the senses; indriya-arthebhyah, from all the objects of the senses; iva, as; kurmah, a tortoise; sarvasah, wholly (withdraws); angani, its limbs, from all sides out of fear; — when the man engaged in steadfastness to Knowledge withdraws thus, then tasya, his; prajna, wisdom; pratisthita, remains established — (the meaning of this portion has already been explained). As to that, [That is , so far as the phenomenal world is concerned.] the organs of a sick person, too, cease to be active when the refrains from sense-objects; they get fully withdrawn like the limbs of a tortoise. but not so the hankering for those objects. How that (hankering) gets completely withdrawn is being stated:

Commentary by Sri Sridhara Swami of Rudra Sampradaya:

Further it is stated that when one withdraws his senses from the objects of the senses such as the ears from sound, the eyes from sight, the tongue from taste and so forth then one becomes steady in wisdom. Regarding the effortless manner in which this withdrawal of the senses is to be enacted is indicated by the example of a turtle withdrawing its limbs within its body.

Commentary by Sri Madhvacharya of Brahma Sampradaya:

Sri Madhvacharya did not comment on this sloka.

Commentary by Sri Keshava Kashmiri of Kumara Sampradaya:

Lord Krishna answers the question, How does such a one sit? With the word yada meaning when, when one is in meditation they do not let their senses go out, for example like the following of sounds by the ear and compels the organs of action to perform only the basic functions of utmost necessity. The illustration used is of the turtle which out of fear of something protects itself by drawing its limbs and head inside its shell. After the danger passes the turtle again lets out its limbs again and in a controlled manner continues on its way. In the same way one who is sthita-prajna situated in the perfect knowledge of transcendent meditation acts thus.

Commentary by Sri Adi Shankaracharya of Advaita Sampradaya:

2.58 And besides, yada, when; ayam, this one, the sannyasin practising steadfastness in Knowledge; samharate, fully withdraws; [‘Fully’ suggests absolute firmness in withdrawal, and ‘withdraws’ suggests full control over the organs] indriyani, the senses; indriya-arthebhyah, from all the objects of the senses; iva, as; kurmah, a tortoise; sarvasah, wholly (withdraws); angani, its limbs, from all sides out of fear; — when the man engaged in steadfastness to Knowledge withdraws thus, then tasya, his; prajna, wisdom; pratisthita, remains established — (the meaning of this portion has already been explained). As to that, [That is , so far as the phenomenal world is concerned.] the organs of a sick person, too, cease to be active when the refrains from sense-objects; they get fully withdrawn like the limbs of a tortoise. but not so the hankering for those objects. How that (hankering) gets completely withdrawn is being stated:

Commentary by Sri Abhinavagupta of Kaula Tantra Sampradaya:

2.58 Yada samharate etc. the nomenclature is not an expression having a composite of both the forces of etymological and traditional meanings, like the word pankaja ‘a lotus’. But it has only the etymological force like the word pacaka ‘a cook’. Whenever he (the sage) withdraws just in his own self-just as a tortoise keeps its limbs in its bossom-from the sense-objects i.e., warding off from the sense-objects, then and then [only] he is man-of-stabilized-intellect. Or [the passage may mean :] Whenever he withdraws, within his own Self, [all], beginning from the sense-objects upto sense-organs i.e., when he approprites in his own Self all in the form of sense-objects and sense-organs. But, how is it that the nomenclature ‘a man-of-stabilized-intellect’ does not hold good in the case of an ascetic ? It is answered-

Sanskrit Shloka Without Transliteration Marks:

yada samharate cayam
kurmo ‘nganiva sarvasah
indriyanindriyarthebhyas
tasya prajna pratisthita

Sanskrit to English Word for Word Meanings:

yadā — when; saḿharate — winds up; ca — also; ayam — he; kūrmaḥ — tortoise; ańgāni — limbs; iva — like; sarvaśaḥ — altogether; indriyāṇi — senses; indriya-arthebhyaḥ — from the sense objects; tasya — his; prajñā — consciousness; pratiṣṭhitā — fixed.