A physical body becomes useless once the life force is gone. The same body, which was lovable to everyone, becomes a liability after death. Everyone wants to dispose it as early as possible as keeping a dead body at home is considered a bad omen.
During the transfer of dead body from one place to another nobody wants to keep the body in a vehicle other than a hearse van, whose job is only to transport dead bodies. No family will be willing to carry the dead body of a person in a car in which the deceased person has been traveling or driving for years.
Be it for any reason, health or rituals, once you touch a dead body you are required to take a bath before you commence your daily routine.
Within a matter of hours, in the absence of life force, the physical body starts disintegrating and in a matter of days, it shows signs of self-destruction and putrefaction.
This vital force is nothing but the soul, aatma, brahma, spirit or consciousness described in different Vedic texts.
Adi Shankaracharya in his book Bhaja Govindam Shloka 6 says:
Yávat-pavano nivasati dehe
távat-pøcChati kusalam gehe,
gatavati váyau dehápáye
bháryá bibhyati tasmin káye. (6)
“Till the life force remains in the body, people come and enquire about your welfare. But, the moment the life force goes out, even your wife is afraid of coming anywhere near your body”.
Life force can be equated to the network of information in computer, radio, television or mobile phone. All these gadgets without data are useless and are thrown away. This silent data, which can be retrieved by operational and application software, represent the life force or soul of these electronic gadgets.
Just as one does not give importance to a computer without data, one should not give importance to the physical body. It is the life force within the body which is respected and cared for and that is what real “I” or “We” is. All glories of the body are only until the life force remains in it.
In Bhagavad Gita, Lord Krishna in Chapter 2 (2.23) says about this life force or ataman: “Fire cannot burn it, weapon cannot cut it, water cannot wet it, air cannot dry it; it is immortal”.
Life force has no dimensions: height, weight, color or image. It is immortal, omnipotent, omniscient and omnipresent. The weight of a live and a dead body immediately after the death is the same.
It is the same life force, which dwells in everybody and during life is modified by actions, memory and desire cycles. If one gets attached to any of the three, one starts getting detached from the soul or the life force. People who are in touch with their life force all the time attain peace and happiness and die young in old age.
Most Vedic mahavakyas say that it is the same spirit, which dwells in everybody and hence every person in the society should be welcomed and treated with equal importance. Aha? Brahmasmi, Tat Tvam Asi, Vasudhaiva Kutumbakam, etc. are few such examples.
According to Adi Shankaracharya, one can achieve nonduality only by seeing God in everyone. Athithi devo bhava is also based on the same principle.