Ahimsa, which is like non-violence or non-harm.

People cause harm to themselves and others in myriad different ways. In Hinduism, there is a concept of The Ladder of Fall:

"By constantly dwelling upon objects, one develops attachment to them; from attachment there arises desire, from desire there is born anger.

From anger there arises delusion, from delusion loss of memory, from loss of memory one loses the function of pure reason, and from the loss of reason one heads towards destruction."

-Bhagavad Gita, Ch. 2, 62-63

It's a very complex subject and is, in my opinion, the core all of Hindu morality. The Buddha says, Life is Suffering. This is because we bring harm to ourselves by attaching ourselves to the things we desire. Not all that you desire can be attained, so you will inevitably suffer by following that path.

The moral path is then to gradually detach your identity from the things you desire and break the cycle of expectation and disappointment while continuing to act in the world as before. How that is done is the subject of the Gita.