“Rahula, all the meditators and brahmins who have purified their physical, verbal and mental actions in the past have done so in this way, by repeatedly reflecting on their physical, verbal and mental actions.”

–Ambalaṭṭhikā Rāhulovāda Sutta MN 61-

This is a passage from a sermon that the Buddha once gave at Rajagriha.

How can we purify the human heart? The Buddha showed us a specific method for doing so.

The words we use in our daily lives and the way we behave all originate from the mind.

Also

"When you are doing a verbal act, you should think about it: 'Is this verbal act that I am doing leading to suffering for myself, for others, or both? Is it an immoral verbal act that has painful consequences, painful consequences?' If, after thinking about it, you find that it is leading to suffering for yourself, for others, or both, then you should stop doing it. But if, after thinking about it, you find that it is not, then you can continue doing it.”

The Buddha teaches that in our everyday conversations, we need to carefully reflect on the words we have spoken and ask ourselves whether they were right or wrong.

Wrong words include, for example, lying to yourself, deceiving others, slandering others, abusive language, speaking badly about what you heard in one place and badly about what you heard in another, and speaking quickly about something completely unrelated to the truth while knowing it so that no one will realize it. Of course, vulgar, dirty words and curses are also included.

Making an effort to avoid using such words in your daily life means that you have to reflect on yourself every day.

And if you want to have a dialogue based on that reflection, you need to chew over your words in your mind before they come out of your mouth, polish them up repeatedly, and then output them. This is the discipline of directing sati to your mind and judging your words with sati.

In the same way, whenever you take any action, whenever you make any movement, whenever you do anything with your hands, feet or whole body, that action too must be reflected upon in the same way.

And from the results of that reflection, when you take your next action, whatever the form it may be, using your whole body and limbs, you must first think carefully about what action will bring about the right result, or the wrong result, and then ponder and consider it, directing sati into your mind.

These three, which come from the mind, mouth and body, are called karma. They are manokamma, vacakamma and kayakamma.

If these karmas are directed in a positive direction and bring about good results, then they are good karma, but if they are directed in a negative direction and cause suffering to both parties, then they are bad karma.

The painful or painful consequences of evil deeds, the consequences that cause some kind of mental disorder, in the next stage give rise to feelings of hatred, anger, sadness, envy, jealousy, etc.

For example, if this is expressed in the form of retaliation by the other person, you who received the retaliation will also feel pain, anger, pain, sadness, and other mental disorders. This will cause you to feel ill will toward the other person in the same way, which will lead to your behavior or the next action. This is the law that calls for a negative chain reaction.

When we fall into this evil dharma, our mind becomes endlessly depressed, heavy, and painful, and we are unable to escape from sorrow and grief. This creates an obstacle in the mind. This is nothing other than the path of attachment, or Byābādha of 5-Nivarana.