Sankhya Yoga 2.24

Verse 2.24 The essence of the principle of atma.

अच्छेद्योऽयमदाह्योऽयमक्लेद्योऽशोष्य एव च |

नित्य: सर्वगत: स्थाणुरचलोऽयं सनातन: || 24||

achchhedyo ’yam adāhyo ’yam akledyo ’śhoṣhya eva cha

nityaḥ sarva-gataḥ sthāṇur achalo ’yaṁ sanātanaḥ

achchhedyaḥ—unbreakable; ayam—this soul; adāhyaḥ—incombustible; ayam—this soul; akledyaḥ—cannot be dampened; aśhoṣhyaḥ—cannot be dried; eva—indeed; cha—and; nityaḥ—everlasting; sarva-gataḥ—all-pervading; sthāṇuḥ—unalterable; achalaḥ—immutable; ayam—this soul; sanātanaḥ—primordial

Atma  is unbreakable and incombustible; it can neither be dampened nor dried. It is everlasting, in all places, unalterable, immutable, and primordial.

In this verse, Krishna says atma is unbreakable and incombustible. It can neither be dampened nor be dried.  A doubt may arise here if atma is a non-existent entity. Because a non-existent entity too cannot be subject to destruction. For example, a hare's horn cannot be destroyed since there is no possibility of a hare to have horns. But atma is not a non-existing entity. It is the only entity that exists. And here Krishna denotes only that atma and not nothingness (Shunya). To know that I exist, I do not require any external means of knowledge such as the senses, anumana (prediction) or by example. Since atma is swatah siddha: self evident, it does not require any external means to reveal itself.  

The reason why Krishna says that atma cannot be broken etc, is to establish that it is not a non-existing entity.

Atma is not limited by time and hence it is nityam, eternal. It is all pervading, sarvagatha: since it is all pervading it is sthanu: fixed. But if it is fixed in one place like the trees, will it be moving while standing in one place? No, it is achala: not moving. Krishna says atma is sanathanam: always present; primordial. Atma is the cause of everything but has no cause for its coming into existence. 

Krishna here uses so many words to describe that atma which cannot be described by words. Upanishads say words cannot reach atma. But the reason for using multiple words to describe the nature of atma is because for a student like Arjuna, any one of those words might enter his heart and make him realize his own self and remove his ignorance and thereby his sorrow. Due to ignorance man brings forth sorrow upon himself and loses his divinity. In order to remove that ignorance Krishna uses a lot of words to explain atma.