SB 3.31.44–In this way the living entity gets a suitable body with a material mind and senses, according to his fruitive activities. When the reaction of his particular activity comes to an end, that end is called death, and when a particular type of reaction begins, that beginning is called birth.
PURPORT-…We can see that because of different reactionary activities, one man is born in a rich family, and another is born in a poor family, although both of them are born in the same place, at the same moment and in the same atmosphere. One who is carrying pious activity with him is given a chance to take his birth in a rich or pious family, and one who is carrying impious activity is given a chance to take birth in a lower, poor family. The change of body means a change to a different field of activities. Similarly, when the body of the boy changes into that of a youth, the boyish activities change into youthful activities.
It is clear that a particular body is given to the living entity for a particular type of activity. This process is going on perpetually, from a time which is impossible to trace out. Vaiṣṇava poets say, therefore, anādi karama-phale, which means that these actions and reactions of one’s activity cannot be traced, for they may even continue from the last millennium of Brahmā’s birth to the next millennium. We have seen the example in the life of Nārada Muni. In one millennium he was the son of a maidservant, and in the next millennium he became a great sage.
Some Conclusions–What is a millennium and how long does it last?
SB 6.10.16 purport…In one day of Brahmā there are fourteen Manus, who each live for seventy-one millenniums. The four yugas—Satya, Tretā, Dvāpara and Kali—constitute one millennium.
And the 4 yugas, Satya Treta Dvarapa and Kali last for 4,300,000 years total. Multiply that total by 71 and you get the lifetime of one Manu. There are 14 Manus who come and go in one day of Lord Brahma.
Srila Prabhupada says above that these karmic reaction we carry with us may have begun even since the time of Lord Brahmas birth, an amount which we simply cannot calculate. In other words, we have been here in material bodies, and not just human ones, for so long it seems and is described like an eternity. And our first birth in this world simply cannot be traced out, it is that long ago. So the point made above is that as long as we perform any activity that is not meant to please Lord Vishnu, or His bona fide representative, then that activity , be it pious or impious, generates Karma for us all.
Just looking at this from a point of energy expended for any activity in this world, and the resultant karmic reactions, the very small material return to us is hardly worth any effort for making material plans for improvement. That is why one great sage, who had a benediction to live for millions of years when asked , why don’t you build yourself a small hut so that the blazing sun wont melt you every day in your meditations? He replied” Why should I— life is so short!!
BG 3.9-Work done as a sacrifice for Visnu has to be performed, otherwise work binds one to this material world. Therefore, O son of Kunti , perform your prescribed duties for His satisfaction, and in that way you will always remain unattached and free from bondage.
Hare Krsna
damaghosa das