Beings are owners of their actions (karma), heirs of their actions; they originate from their actions, are related to their actions, and have their actions as their refuge. It is action that distinguishes beings as inferior and superior. - The Buddha
What we do, say, and think—karma—leaves traces. Those traces don't disappear. They shape what comes next, sometimes in ways we don't remember, but that still echoes in this life.
By oneself is evil done, by oneself is one defiled. By oneself is evil left undone, by oneself is one purified. Purity and impurity depend on oneself—no one can purify another. (The Dhammapada, 165)
Buddhist's Five Precepts
1. I do not kill.
2. I do not steal.
3. I do not commit sexual misdeeds.
4. I do not speak falsehood.
5. I do not take intoxicants (alcohol, drugs, or cigarettes).
Buddhists must adhere to the Noble Eightfold Path to reach the ultimate liberation, nirvana. What is The Noble Eightfold Path? Buddha’s Guide To Enlightenment