The Avatamsaka (Flower Adornment) Sutra says:

They fully realize that the various differences among living beings
Arise entirely from distinctions in their thoughts 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,
Out of pity for all living beings,
So as to cause them to properly contemplate true Dharma.

Living 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 Condition-Enlightened Ones, they become Condition-Enlightened Ones. If they plant the causes for being Hearers, they become Hearers. These 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 is neither superstitious nor off by the least little bit.

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 end the process of cause and effect. Ordinary people continue to create causes and undergo effects. They commit offenses for no reason and then refuse to acknowledge them, insisting they have done nothing wrong. Their lack of shame and conscience compounds their offenses and eliminates the possibility of forgiveness.

There are various living beings, each with good and bad seeds. Each being creates its karma and undergoes its individual retribution. These differences arise from distinctions in the five skandhas of form, feeling, thinking, formations, 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 living beings, they cultivate the Bodhisattva conduct and dedicate all their accumulated good roots to them. Bodhisattvas see living beings doing foolish things and so try to teach them, but living beings are very deluded and do not understand.

Bodhisattvas teach living beings to give themselves up for others, to renounce the superficial and seek the profound, to support and perpetuate the Proper Dharma, but living beings don't listen. That's why living beings 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.