After Kurukshetra war, Dhritrarashtra asked Krishna, “I had 100 sons. All of them were killed. Why? Krishna replied, “50 lifetimes ago, you were a hunter. While hunting, you tried to shoot a male bird. It flew away. In anger, you ruthlessly slaughtered the 100 baby birds in the nest. Father-bird had to watch in helpless agony. Because you caused that father-bird the pain of seeing the death of his 100 sons, you too had to bear the pain of your 100 sons dying.... Dhritarastra said, “Ok, but why did I have to wait for fifty lifetimes?” Krishna answered, “You were accumulating punya (pious credits) during the last fifty lifetimes to get 100 sons - because that requires a lot of punya. Then you got the reaction for the papa (sin) that you have done fifty lifetimes ago.” Krishna says in the Bhagavad-gita (4.17) "gahana karmano gatih". The way in which action and reaction works is very complex. God knows best which reaction has to be given at what time in what condition. Ther