Friendly Goodwill is the 9th Mental Perfection:

Friendliness means Care, Support, Concern, Goodwill, Kindness,
& Sympathy.
Friendliness means Symbiosis, Mutual Aid, Assistance,
and keen Compassion.
Friendliness means Cooperation, Helpfulness, Benevolence, Mutual Advantage!
Only friendliness can completely evaporate the poison of
anger and hot hate!
Its characteristic
is to promote the welfare of others,
its function
is to do
only good, and its manifestation is kindness, sympathy, and
calm gentleness...
The proximate cause of friendliness is seeing the good
aspects of things.
The proximate cause of understanding
compassion is this very friendliness.

The Blessed Buddha said about friendliness (Mettā):
"Bhikkhus, whatever kinds of worldly merit there are, all are not
worth one
sixteenth part of the release of mind by universal friendliness in shining,
glowing, and beaming radiance.
This release of mind by universal friendliness
far excels, and surpasses them all..."
What are the 11 Advantages of cultivating such Universal Friendliness?
The 4 Brahma
Viharas; The 4 Divine States: The 4 Infinite States:
"Friends, eleven advantages are to be expected as effects from the release
of mind into friendliness by the practice of goodwill, by cultivating amity,
by making much of it frequently, by making friendliness the vehicle, the tool,
the basis, by insisting on it, by being well established
in it as a sublime habit:
What are these eleven advantages ?
One falls asleep well. One wakes up Happy. One dreams
no evil dreams.
One is
liked, and loved by all human beings.
One is liked, and loved by all
non-human beings too.
One is
guarded, and protected by the divine devas.
One cannot be harmed by fire,
poison, or weapons.
One easily attains the concentration
of absorption.
One's appearance becomes serene, calm, and
composed.
One dies without confusion, bewilderment, or
panic.
One reappears after death on the Brahma level, if one
has penetrated to no higher level in this very life....
When the mind is released into friendliness by the practice of
goodwill,
by manifesting friendliness, by cultivating amity, by frequently making much
of it, by making friendliness the vehicle, the tool, the basis, the
medium, the
foundation, by persisting in it, by insisting on it, by properly
consolidating it,
by thoroughly undertaking it, by making it a familiar supreme habit, by so
being well established in it, these eleven blessings can be expected."
Anguttara
Nikāya V 342

There, Oh friends, the Bhikkhu with a mind full of friendly
loving-kindness
pervading first one direction, then a 2nd one, then a 3rd one, then the
4th one,
as below so above, across and all around, everywhere identifying himself
with
all sentient beings, he is encompassing the whole world with a mind of
friendly
loving-kindness, with a wide mind, vast, refined, unbounded, cleared, exalted,
pure and bright, free from all hate, and free from all ill will ...
There, Oh friends, the Bhikkhu with a mind full of understanding compassion
pervading first the front, then the right side, then the back, then the left
side,
as above so below, across, and all around, all over, far and wide; identifying himself
with all sentient beings, he is perfusing the whole universe with a mind imbued
with pity, with a spacious mind, a refined mind, infinite, purified, all
luminous,
freed from all anger, and freed from any trace of enmity ...
Then, the
Bhikkhu with a mind full of altruistic, sympathetic, and mutual
Joy
pervades the North, then the East, then the South, then the West, as below
so above, across, and all around, universally, infinitely; identifying himself with
all sentient beings, he is suffusing all galaxies with a mind elevated by genuine
mutual, and altruistic sympathetic joy, with an open mind, immeasurable, wide,
limitless, pure
and shining, free from all aversion, and free from all bitterness ...
Finally, Oh friends, the Bhikkhu with a mind full of balanced equanimity
is finally
pervading first the frontal quadrant, then the right, then the rear, and then the
left
quadrant, as below, so above, across, and all around, everywhere associating
himself with
all sentient beings, he is permeating the whole world with a mind
satiated
with
stilled, and balanced equanimity, calmed, with a mountain-like mind,
cultivated, endless, clean, dazzling, freed from any irritation, and resentment."

"So too, Bhikkhus, others may speak to you timely
or untimely,
truly
or untruly,
gently
or harshly, beneficially or harmfully,
based on kindness, or on bitter hate.
If they abuse you verbally, you should train yourselves in this way:
"Our minds will remain unaffected, we shall speak no angry words, will
dwell
friendly and understanding, with thoughts of kindness, and no inward
anger.
We shall remain friendly and beam goodwill towards that very person, and we
shall dwell extending it to the entire universe, mentally overflowing,
exalted,
measureless and infinite in friendliness, without any trace hostility or
ill-will."
That is how you should train yourselves. Even if bandits were savagely to cut
you up, limb by limb, with a two-handled saw, one who harbors hate on that
account, would not be one, who carried out my teaching. Bhikkhus, you should
keep this instruction on this
Simile of the Saw constantly in mind..."
Majjhima
Nikāya, Sutta 21
Thus he who both day and night takes delight in harmlessness,
sharing love with all that lives, finds enmity with none...
Samyutta
Nikāya. I 208
When one with a mind of love feels
compassion for the entire universe
above, below, and across, this
mind is unlimited everywhere.
Jātaka 37


The Bodhisatta once was born as the righteous
King Ekaraja (The unique King).
His
kingdom was taken by force. He and his son were buried in a pit to the neck...
King Ekaraja, however neither resisted, nor bore even slight ill will against
the
invaders. Later he remembered this as his ultimate perfection of friendliness.
Ekaraja Jātaka 303
On this
Divine Praxis of Loving-Kindness (Mettā):
https://What-Buddha-Said.net/library/Wheels/wh006.pdf
Video on
Mettā Meditation on Friendliness:
How to cure Depression?
https://www.youtube.com/watch?v=yz0nE1wRWQY

On Universal
Friendliness:
https://What-Buddha-Said.net/drops/Metta.htm
https://What-Buddha-Said.net/drops/IV/Good-Will_Again.htm
https://What-Buddha-Said.net/drops/IV/Bon_Benevolence.htm
https://What-Buddha-Said.net/drops/III/Goodwill_Encore.htm
https://What-Buddha-Said.net/drops/IV/Released_by_GoodWill.htm
https://What-Buddha-Said.net/drops/IV/All-Embracing_Kindness.htm
https://What-Buddha-Said.net/drops/IV/Infinite_and_Divine_Classic.htm
https://What-Buddha-Said.net/drops/The_Buddha_on_Noble_Friendship.htm
More on the 10 mental perfections (paramis):
https://What-Buddha-Said.net/drops/IV/The_Ten_Perfections.htm