I. The fruition

1. How what is exalted, true and good is established

Now, teaching the fruition of the four immeasurables, the following words explain what is like:

There are four fruitions of doing this meditation.
By ripening we gain the exalted and truly good.
In the realm we wish, we have a divine or human body,
In a situation producing goodness and benefit.

Those who do not attain an exalted state attain the body of a god or a human being. They perfect the two accumulations, benefit beings, and become inseparable from the four immeasurables. Even if they are careless or fall asleep, they will not fall prey to serious harm. The Ornament of Mahayana Sutras says:

Having the mind of these four Brahma-viharas We will always take birth in the realm we desire. Because they perfect the two accumulations, They produce ripening for sentient beings.

Never separated from purity,
They are free from what does not in accord with them.
Being careless, which is such a condition,
As well as impatience, will never be found there.

As the ultimate fruition, enlightenment is established. The same text says:

What is harmful is banished, and, with seeds of enlightenment,
Happiness is produced and the cause of longing desire.
The essence ripens, and children of the Victorious One,
Relying on Dharma, are not far off from being buddhas.

Abandoning what is harmful is a fruition of separation.

Producing the seed of liberation is a fruition of the predominant condition of empowerment by the master. Being patient about our own trials and hardships, because we are producing happiness for others, is a fruition of production. By meditating on these four in this life, they ripen in other lives as a fruition according with the cause. The nature of these four immeasurables always arises in children of the Victorious One. It is born from previous familiarity, from seeing its objects, and by seeing the faults of what does not conform to them. The same text says

This kindness, having the nature of compassion,
Attains the nature and true discrimination
By former acquaintance and also purification
Of the non-according condition that would spoil it.

2. The benefits of according with the cause

From the two sections of the fruition according with the cause:

a. General

From according with the cause, these themselves are produced.
The good experience gained is free from its opposite side.

By action according with the cause, we always spend our time meditating on the four immeasurables. By experience according with the cause malice, harmfulness, unhappiness, passion, loving and hating will be absent. Now there are the benefits of the power of this.

b. The benefits of the decisive condition As for the decisive condition or power:

The power is birth in a pleasant, happy, and joyful country,
Where there are compatible people and amenities of wealth.

By kindness we are born in a pleasant country, by compassion in a happy one, and by joy in a joyful one with many flowers, medicinal herbs, and so forth. By equanimity we are born among many compatible people and are not harmed.

3. The benefits of doing this

For such a person:

By doing this, these four will grow immensely greater.
The wealth of the two benefits for self and others
At this time becomes completely spontaneous.

By performing this, the four immeasurables increase immensely, growing greater and greater. By that the wealth of the two benefits for oneself and others is spontaneously present. By the increase of the meritorious karma of meditating on these four immeasurables, happiness and goodness are established.

4. The benefit of kindness

Moreover

When perfect enjoyment of kindness is without aggression,
Then the mirror-like wisdom will have been fully attained, 
As sambhogakaya adorned with the major and minor marks.

After kindness transforms aggression into the mirror-like wisdom, sambhogakaya is attained. The Lotus Peak (padma rtse mo) says:

By kindness aggression will be purified
As mirror-like wisdom and sambhogakaya.

5. The benefit of compassion

When compassion is desireless, there is dharmakaya,
Producing the manifestation of discriminating wisdom,
With dharmakaya’s exclusive dharmas, like the ten powers.

Compassion pure of desire is discriminating awareness wisdom and dharmakaya. The same text says:

By compassion desire is fully purified
As discriminating wisdom and ultimate dharmakaya.

6. The benefits of joy

When joy eliminates jealousy, there is nirmanakaya.
The holy all-accomplishing wisdom is attained.
Nirmanakaya is nothing fixed, but of various forms.
This self-existing kaya is spontaneous in its action.

By immeasurable joy we attain the all-accomplishing wisdom, whose nature is perfect buddha activity. Purifying jealousy makes nirmanakaya manifest. The same text says:

By joy all jealousy is fully purified,
As all-accomplishing wisdom and nirmanakaya.
Action becomes spontaneous and excellent.

7. The benefits of equanimity

When equanimity has eliminated pride,
As well as stupidity, there is the essence of things.
Through equality, dharmadhatu wisdom will manifest.
The simplicity of dharmata is svabhavikakaya.

When equanimity has purified pride and ignorance, the wisdom of equality and the dharmadhatu wisdom are established. Svabhavikakaya, the unchanging vajrakaya and the kaya of the manifestation of enlightenment are apprehended. The same text says:

By equanimity and great equanimity
Pride, with envy and ignorance, will be purified.
We master the dharmadhatu and equality wisdoms,
The kaya of manifestation and the vajrakaya.

As for the nature of passionlessness that arises from the four actions of these four immeasurables, the Ornament of Mahayana Sutras says:

Those who have kindness completed by compassion,
If they do not desire to dwell in peace,
Why even speak of worldly happiness
Or enhancing their personal lives and their careers?

As for their not desiring their own happiness, the same text says:

Compassion is made to suffer by those who have suffering.
If that moisture were not produced, who would make them happy?
After the kind produce these others’ happiness,
Their personal happiness is not produced like that.

As for the kind subjugating their own happiness to that of others, the same text says:

The suffering that is produced by kindness
Overwhelms all worldly happiness.
If those who are givers of benefit are without it,
What greater wonder could there be than that?

The Letter to a Student says:

For beings with many unbearable sufferings, without a refuge and helpless,
Those who are happy to suffer in helping others are said to be excellent beings.
The instant that others’ hunger and thirst is completely removed, and they have done it,
They become joyful people. Who indeed could be compared to them?

These diligent ones who so delight in working to benefit others and make them happy,
How could they ever devote themselves to enjoyment in the higher realms?
They will never gain joy by happy youth, nor the trappings of wealth and power,
Nor by spouses or other relationships, nor will they be born among gods or jealous gods.

As for the action of samsara not arising, the former text says:

Compassion, the highest attitude, lacks ego and the nature
Of suffering that comes from samsaric labeling.
It lacks the suffering that comes from consciousness.
Nor will there be the serious harm that comes from wrongdoing

As for the immeasurables of holy beings who have these immeasurably, they transcend the world and are without faults. The same text says:

Those who have desire have corresponding faults.
Those without it, beyond the world, do not possess them. Those who have this attitude, by their loving-kindness, Will be without any faults and go beyond the world.

Those who are kind to their literal fathers, mothers, and children have desire. Bodhisattvas have no such desires in regard to sentient beings. This is because they are liberated from samsara. They lack faults because they liberate suffering sentient beings from samsara. The same text says:

Not knowing how to cross the great waves of suffering,
As for those that put their reliance in the great darkness,
The sorts of means that are employed by worldly leaders,
How is it possible that they would not have faults?

The same text says:

If worldly enlightened ones and all the arhats
Among the pratyekabuddhas lack this kindness,
It is needless even to speak of any others;
But world-transcending ones are not like that.

If we do not meditate on the four immeasurables, there will be many faults. The same text says:

A bodhisattva who possesses ill-will 
And malice due to pain and unhappiness,
Resulting from attachments of desire,
Is sure to come in contact with many faults.

As for its being said that those born in the desire realms have attachments of desire, those who are born in the first two realms of desire and form are said to have samsaric desire. The Abhidharmakosha says:

Those born in those two realms have attachments of samsaric desire.

As for the fault of increasing kleshas being immeasurable. the former text says:

Kleshas conquer the self. They conquer beings. They conquer discipline.
By receiving corruption, we are debased and become samsaric. Teachers of such things degrade us.
Do not listen to their arguments. They will be born in other lives as beings without the freedoms.
Harmed by attaining and non-attaining, their minds will attain great suffering.

Attainment corrupts the happiness of this life, and non-attainment corrupts later happiness. As for the benefits of meditating on the four immeasurables, we do not have such faults, we grasp the possibilities of benefiting beings, and since we are not whirled about in samsara by the kleshas, suffering does not arise. The same text says:

For those who rest in kindness and the rest,
The faults that were described do not arise.
Having no kleshas, they will benefit beings,
And will not pass into samsaric birth.

8. The praise of their virtues:

As to what they^[1] are like:

These, kindness and so forth are given the highest praise
By the one who is the teacher of gods and human beings
As having limitless virtues and being beyond compare.

The Glorious Garland Sutra (dpal phreng gi mdo) says:

Whoever meditates on the four immeasurables
Will be considered with kindness by all the tathagatas.
All the immeasurable good qualities of this
Are even more limitless than endless space itself

9. The four immeasurables are the way of the victorious ones

As for the four immeasurables:

Any path that is without them is in error.
Refuge in other teachers is an inferior path.
The path that has them leads to spotless liberation.
This is the way that was traveled by buddhas of the past.
It also will be traveled by those who are to come.

The Commentary of the Praise of the Bhumis says:

The four immeasurables are the path of liberation. Others paths are wrong.

10) How to attain the two ultimate realities.

The causal vehicles hold that, like seeds producing sprouts,
Upaya and prajña are the producers of the two kayas.
The fruition vehicles proclaim them as being mere conditions,
Removing the two obscurations that veil these same two kayas .
But since upaya depends on the limitless path of compassion,
The meaning is the same, compassionate emptiness.
In that, both cause and fruition practice are in accord.

The vehicles of characteristics mostly proclaim that the two accumulations are the producing cause of the two kayas . The Sixty Stanzas on Reasoning (rig pa drug bcu pa) says:

By this merit all beings
Accumulate merit and wisdom.
May we gain the two ultimates
Arising from merit and wisdom.

In secret mantra, it is maintained that clearing away the two obscurations of the kayas occurs through practicing the two accumulations with profound upaya and prajña.  Therefore such practice is proclaimed to be a condition of this clearing away. Both are in accord, insofar as practice has the essence of emptiness and compassion.

11. Summarizing the meaning of this meditation

The sutras say that the unborn seeds of happiness
Have existed primordially and never were created.
The mantrayana accords with this, because it claims
To clear away the incidental obscurations
That are the primordial obscurations of trikaya.

To summarize briefly, learned and accomplished ones
Explain that sutra and tantra are a unity,
As outer and inner aspects of a single path.

Therefore, following after the Buddha’s genuine children,
We should strive to practice the four immeasurables.

The Buddha’s final teaching says that the dhatu is naturally pure and possesses the buddha qualities primordially. However, at the time of practicing the path, the buddha qualities appear to arise, and are proclaimed to appear. In mantrayana all beings naturally exist  as the mandala, as explained below. Since these two approaches are without distinction, it amounts to the same thing. In the path, the two accumulations of upaya and prajña are also the same. In the fruition, the kayas and wisdoms are the same. Former great masters like Padmasambhava have explained their relationship as inner and outer. Therefore, we should strive to meditate on the four immeasurables.

Footnotes and references:

[1]:

The immeasurables.