nainaḿ chindanti śastrāṇi
nainaḿ dahati pāvakaḥ
na cainaḿ kledayanty āpo
na śoṣayati mārutaḥ

Translation of Bhagavad Gita 2.23

The soul can never be cut to pieces by any weapon, nor burned by fire, nor moistened by water, nor withered by the wind.

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

All kinds of weapons—swords, flame weapons, rain weapons, tornado weapons, etc.—are unable to kill the spirit soul. It appears that there were many kinds of weapons made of earth, water, air, ether, etc., in addition to the modern weapons of fire. Even the nuclear weapons of the modern age are classified as fire weapons, but formerly there were other weapons made of all different types of material elements. Firearms were counteracted by water weapons, which are now unknown to modern science. Nor do modern scientists have knowledge of tornado weapons. Nonetheless, the soul can never be cut into pieces, nor annihilated by any number of weapons, regardless of scientific devices.

The Mayavadi cannot explain how the individual soul came into existence simply by ignorance and consequently became covered by illusory energy. Nor was it ever possible to cut the individual souls from the original Supreme Soul; rather, the individual souls are eternally separated parts of the Supreme Soul. Because they are atomic individual souls eternally (sanatana), they are prone to be covered by the illusory energy, and thus they become separated from the association of the Supreme Lord, just as the sparks of a fire, although one in quality with the fire, are prone to be extinguished when out of the fire. In the Varaha Purana, the living entities are described as separated parts and parcels of the Supreme. They are eternally so, according to the Bhagavad-gita also. So, even after being liberated from illusion, the living entity remains a separate identity, as is evident from the teachings of the Lord to Arjuna. Arjuna became liberated by the knowledge received from Krishna, but he never became one with Krishna.Commentary by Sri Vishvanatha Chakravarthi Thakur of Gaudiya Sampradaya:

Also, it is not possible to injure the soul at all by the weapons used by you in the battle. That is explained in this verse. Weapons such as swords cannot cut it. The fire weapon cannot burn it. The rain weapon cannot wet it, nor can the wind weapon dry it out.Commentary by Sri Ramanuja of Sri Sampradaya:

2.23 – 2.24 Weapons, fire, water and air are incapable of cleaving, burning, wetting and drying the self; for, the nature of the self is to pervade all elements; It is present everywhere; for, It is subtler than all the elements; It is not capable of being pervaded by them; and cleaving, burning, wetting and drying are actions which can take place only by pervading a substance. Therefore the self is eternal. It is stable, immovable and primeval. The meaning is that It is unchanging, unshakable and ancient.
Commentary by Sri Sridhara Swami of Rudra Sampradaya:

The imperishable nature of the eternal soul is being explicitly proven by showing the impossibility of any means to slay it by these examples in answer to the previous statement of how can the eternal soul be slain in any way?
Commentary by Sri Madhvacharya of Brahma Sampradaya:

In the normal course of events in the material existence although there is no destruction there may appear that some being is destroyed like in the case of Daksa losing his head due to the wrath of Siva. To avoid misinterpretations in this way the Supreme Lord mentions the fact that the soul can not be pierced in any way.

Now begins the summation.

As there is no means for the destruction of the Supreme Lord there is also no means of destruction for the immortal soul.
Commentary by Sri Keshava Kashmiri of Kumara Sampradaya:

It could be interjected that just as in a burning house the occupants of the house are burned along with it, so also in the case of the soul if the physical body is burnt or cut might not the soul be burnt or cut as well. To annihilate this misconception the Supreme Lord Krishna expains that never can the soul be cut by weapons, never can the soul be burned by fire, never can the soul be moistened by water and never can the soul be withered by air. Although only one use of the word na meaning never would have been sufficient to establish the premise of utter futility in trying to destroy the soul, it is used four times to strengthen the empasis insuring there is not even the slightest vestige of doubt.
Commentary by Sri Adi Shankaracharya of Advaita Sampradaya:

2.23 Why does It verily remain unchanged? This is being answered in, ‘Weapons do not cut It,’ etc. Sastrani, weapons; na, do not; chindanti, cut; enam, It, the embodied one under discussion. It being partless, weapons like sword etc. do not cut off Its limbs. So also, even pavakah, fire; na dahati enam, does not burn, does not reduce It to ashes. Ca, and similarly; apah, water; na enam kledayanti, does not moisten It. For water has the power of disintegrating a substance that has parts, by the process of moistening it. That is not possible in the case of the partless Self. Similarly, air destroys an oil substance by drying up the oil. Even marutah, air; na sosayati, does not dry; (enam, It,) one’s own Self. [Ast. reads ‘enam tu atmanam, but this Self’, in place of enam svatmanam.-Tr.]
Commentary by Sri Abhinavagupta of Kaula Tantra Sampradaya:    

2.23 See Comment under 2.25
Sanskrit Shloka Without Transliteration Marks:

nainam chindanti sastrani
nainam dahati pavakah
na cainam kledayanty apo
na sosayati marutah
Sanskrit to English Word for Word Meanings:

na — never; enam — this soul; chindanti — can cut to pieces; śastrāṇi — weapons; na — never; enam — this soul; dahati — burns; pāvakaḥ — fire; na — never; ca — also; enam — this soul; kledayanti — moistens; āpaḥ — water; na — never; śoṣayati — dries; mārutaḥ — wind.