The Avatamsaka (Flower Adornment) Sutra says:

They fully realize that the various differences among beings
Arise entirely from distinctions in their thinking and activities.
Contemplating thus, they perceive with clarity
The nature of all dharmas without harming it.
The wise ones fathom the Dharma of all Buddhas.
They dedicate the merit from their practice of it,
Empathizing with all beings,
And thus enabling them to properly contemplate
dharmas as they actually are.

Beings become deluded, create karma, and undergo retribution. They plant causes and then reap the corresponding results. This is a natural principle. If they plant the causes for being Buddhas, they reap the result of Buddhahood. If they plant the causes for being Bodhisattvas, they reap the result of Bodhisattvahood. If they plant the causes for being Ones Enlightened by Conditions, they become Ones Enlightened by Conditions. If they plant the causes for being Hearers, they become Hearers. Those are the Four Sagely Realms.

The Six Common Realms are the Three Good Realms of gods, humans, and asuras, and the Three Evil Realms of animals, hungry ghosts, and hell-beings. In general, if one plants the causes for the Three Good Realms, one is reborn in these realms. The same applies to the Three Evil Realms. The principle of cause and effect never off by the least bit. It is not a superstition.

Not knowing the seriousness of cause and effect, deluded people casually make mistakes in cause and effect or even deny the law of cause and effect. Wise people, knowing that the law of cause and effect relentlessly metes out the deserved retribution, dare not make mistakes in cause and effect. They always consider carefully before doing anything. Sages cultivate in order to understand the process of cause and effect. Ordinary people continue to create causes and undergo effects. Originally their offenses did not exist until they committed them. Once they have committed them, they refuse to acknowledge them as offenses, insisting they have done nothing wrong. Being devoid of shame and conscience compounds their offenses beyond the point of forgiveness.

Beings are different in various ways, including the good and bad seeds they possess.Each being creates its karma and undergoes its individual retribution. This process evolves from distinctions that occur in the five skandhas of form, feeling, thinking, activities, and consciousness. If one can contemplate and appreciate the various karmic retributions, one will fathom the nature of all dharmas without destroying it.

Wise people clearly understand all the Dharmas spoken by the Buddhas. Out of pity for beings, they cultivate the Bodhisattva conduct and dedicate all their accumulated good roots to them. Bodhisattvas see beings doing foolish things and so try to teach them, but beings are very deluded and do not understand.

Bodhisattvas teach beings to make sacrifices for the sake of others, to renounce the superficial aspects and seek the root of the matter, and to support and protect the Proper Dharma so that it will long abide in the world. But beings lack faith. That's why they are to be pitied. They should be exhorted to refrain from all evil and to practice all good. We should try to practice in accord with the true Dharma, constantly reflecting and asking ourselves: "Have we made mistakes in cause and effect? Instead of fulfilling our responsibilities within Buddhism, have we created all kinds of offenses?" We should constantly look within and examine ourselves again and again. Only then can we be considered genuine Buddhists.