Mbh 3.208.2a

It is seen that able, intelligent and diligent persons are baffled in their efforts, and do not attain the fruits of their actions. On the other hand, persons who are always active in injuring others and in practising deception on the world, lead a happy life. There are some who attain prosperity without any exertion. And there are others, who with the utmost exertion, are unable to achieve their dues. Miserly persons with the object of having sons born to them worship the gods, and practise severe austerities, and those sons having remained in the womb for ten months at length turn out to be very infamous issue of their race; and others begotten under the same auspices, decently pass their lives in luxury with heaps of riches and grain accumulated by their ancestors. The diseases from which man suffer, are undoubtedly the result of their own karma. They then behave like small deer at the hands of hunters, and they are racked with mental troubles. And, O Brahmana, as hunters intercept the flight of their game, the progress of those diseases is checked by able and skilful physicians with their collections of drugs. And, the best of the cherishers of religion, thou hast observed that those who have it in their power to enjoy (the good things of this earth), are prevented from doing so from the fact of their suffering from chronic bowel-complaints, and that many others that are strong and powerful, suffer from misery, and are enabled with great difficulty to obtain a livelihood; and that every man is thus helpless, overcome by misery and illusion, and again and again tossed and overpowered by the powerful current of his own actions (karma). If there were absolute freedom of action, no creature would die, none would be subject to decay, or await his evil doom, and everybody would attain the object of his desire.