KARMA

What a man turns out to be depends on how he acts and on how he conducts himself. If his actions are good, he will turn into something good. If his actions are bad, he will turn into something bad.
A man turns into something good by good action and into something bad by bad action. And so people say: “A person here consists simply of desire.” A man resolves in accordance with his desire, acts in accordance with his resolve, and turns out to be in accordance with his action.’ (Brihad  Aranyaka Upanishad 4.4.3-5)

Commentary by Nick Sutton

What is then that dictates the actions we perform? Why does one person pursue the path of virtue and another the path of perdition? The answer given here is the same as that given by Krishna in the Bhagavad Gita (3.37): it is kama, or desire. For Krishna it is selfish desire that is the root of sin and the cause of anger, but the Brihad Aranyaka Upanishad explains the matter in a slightly different
way. It notes that desire shapes resolve (kratuh) and one’s resolve determines the actions one
performs. The point here is really quite simple, though it is fundamental to our understanding
of the doctrine of karma and of good and evil. If one’s desire (kama) is to be righteous, then
one first resolves to follow a virtuous life and then undertakes the virtuous actions (punya)
that lead to a pleasant future destiny. But if one’s desire is simply to enjoy pleasure through
the senses, then one’s resolve follows this desire and one is impelled to perform the wicked
acts that are required for unrestricted sensual pleasures. So for the Upanishad here, kama or
desire is not to be condemned universally. Rather it is the direction of one’s desires that is the
key point in determining the nature of one’s actions and the future destiny shaped by these
actions.