Mahabharata 3.32.34

3.32.34

naitāni veda yaḥ kaścinmuhyantyatra prajā imāḥ |
rakṣyāṇyetāni devānāṃ gūḍhamāyā hi devatāḥ || 34 ||

If asceticism, the austerities of celibate life, sacrifices, study of the Vedas, charity, honesty,--these all were fruitless, men would not have practised virtue generation after generation. If acts were all fruitless, a dire confusion would ensue. For what then do Rishis and gods and Gandharvas and Rakshasas who are all independent of human conditions, cherish virtue with such affection? Knowing it for certain that God is the giver of fruits in respect of virtue, they practise virtue in this world. This, O Krishna, is the eternal (source of) prosperity. When the fruits of both knowledge and asceticism are seen, virtue and vice cannot be fruitless. Call to thy mind, O Krishna, the circumstances of thy own birth as thou that heard of them, and recall also the manner in which Dhrishtadyumna of great prowess was born! These, O thou of sweet smiles, are the best proofs (of the fruits of virtue)! They that have their minds under control, reap the fruits of their acts and are content with little. Ignorant fools are not content with even that much they get (here), because they have no happiness born of virtue to acquire to in the world hereafter. The fruitlessness of virtuous acts ordained in the Vedas, as also of all transgressions, the origin and destruction of acts are, O beautiful one, mysterious even to the gods. These are not known to any body and everybody. Ordinary men are ignorant in respect of these.

The gods keep up the mystery, for the illusion covering the conduct of the gods is unintelligible. Those regenerate ones that have destroyed all aspirations, that have built all their hopes on vows and asceticism, that have burnt all their sins and have acquired minds where quest and peace and holiness dwell, understand all these. Therefore, though you mayst not see the fruits of virtue, thou shouldst not yet doubt religion or gods. Thou must perform sacrifices with a will, and practise charity without insolence. Acts in this world have their fruits, and virtue also is eternal. Brahma himself told this unto his (spiritual) sons, as testified to by Kashyapa. Let thy doubt, therefore, O Krishna, be dispelled like mist. Reflecting upon all this, let thy scepticism give way to faith. Slander not God, who is the lord of all creatures. Learn how to know him. Bow down unto him. Let not thy mind be such. And, O Krishna, never disregard that Supreme Being through whose grace mortal man, by piety, acquireth immortality!'"