The living entity is sanatana, eternal. Because he cannot be killed by any weapon, burnt into ashes by fire, soaked or moistened by water, nor dried up by air, he is considered to be immune to material reactions

Expressions researched:
"The living entity is sanatana, eternal. Because he cannot be killed by any weapon, burnt into ashes by fire, soaked or moistened by water, nor dried up by air, he is considered to be immune to material reactions"

SB Canto 4

The living entity is sanātana, eternal. Because he cannot be killed by any weapon, burnt into ashes by fire, soaked or moistened by water, nor dried up by air, he is considered to be immune to material reactions. Although he is changing bodies, he is not affected by the material conditions. He is placed under the material conditions, and he acts according to the directions of his friend, the Supersoul.

SB 4.25.10, Translation and Purport:

My dear King, once in the past lived a king named Purañjana, who was celebrated for his great activities. He had a friend named Avijñāta ("the unknown one"). No one could understand the activities of Avijñāta.

Every living entity is purañjana. The word puram means "within this body, within this form," and jana means "living entity." Thus everyone is purañjana. Every living entity is supposed to be the king of his body because the living entity is given full freedom to use his body as he likes. He usually engages his body for sense gratification, because one who is in the bodily conception of life feels that the ultimate goal of life is to serve the senses. This is the process of karma-kāṇḍa. One who has no inner knowledge, who does not know that he is actually the spirit soul living within the body, who is simply enamored by the dictation of the senses, is called a materialist. A materialistic person interested in sense gratification can be called a purañjana. Because such a materialistic person utilizes his senses according to his whims, he may also be called a king. An irresponsible king takes the royal position to be his personal property and misuses his treasury for sense gratification.

The word bṛhac-chravāḥ is also significant. The word śravaḥ means "fame." The living entity is famous from ancient times, for as stated in Bhagavad-gītā (2.20), na jāyate mriyate vā: "The living entity is never born and never dies." Because he is eternal, his activities are eternal, although they are performed in different types of bodies. Na hanyate hanyamāne śarīre: (BG 2.20) "He does not die, even after the annihilation of the body." Thus the living entity transmigrates from one body to another and performs various activities. In each body the living entity performs so many acts. Sometimes he becomes a great hero—just like Hiraṇyakaśipu and Kaṁsa or, in the modern age, Napoleon or Hitler. The activities of such men are certainly very great, but as soon as their bodies are finished, everything else is finished. Then they remain in name only. Therefore a living entity may be called bṛhac-chravāḥ; he may have a great reputation for various types of activities. Nonetheless, he has a friend whom he does not know. Materialistic persons do not understand that God is present as the Supersoul, who is situated within the heart of every living entity. Although the Paramātmā sits beside the jīvātmā as a friend, the jīvātmā, or living entity, does not know it. Consequently he is described as avijñāta-sakhā, meaning "one who has an unknown friend." The word avijñāta-ceṣṭitaḥ is also significant because a living entity works hard under the direction of the Paramātmā and is carried away by the laws of nature. Nonetheless, he thinks himself independent of God and independent of the stringent laws of material nature. It is stated in Bhagavad-gītā (2.24):

acchedyo 'yam adāhyo 'yam

akledyo 'śoṣya eva ca

nityaḥ sarva-gataḥ sthāṇur

acalo 'yaṁ sanātanaḥ

"This individual soul is unbreakable and insoluble and can be neither burned nor dried. He is everlasting, all-pervading, unchangeable, immovable and eternally the same."

The living entity is sanātana, eternal. Because he cannot be killed by any weapon, burnt into ashes by fire, soaked or moistened by water, nor dried up by air, he is considered to be immune to material reactions. Although he is changing bodies, he is not affected by the material conditions. He is placed under the material conditions, and he acts according to the directions of his friend, the Supersoul. As stated in Bhagavad-gītā (15.15):

sarvasya cāhaṁ hṛdi sanniviṣṭo

mattaḥ smṛtir jñānam apohanaṁ ca

"I am seated in everyone's heart, and from Me come remembrance, knowledge and forgetfulness." Thus the Lord as Paramātmā is situated in everyone's heart, and He gives directions to the living entity to act in whatever way the living entity desires. In this life and in his previous lives the living entity does not know that the Lord is giving him a chance to fulfill all kinds of desires. No one can fulfill any desire without the sanction of the Lord. All the facilities given by the Lord are unknown to the conditioned soul.