In essence: “Do unto others as you would have them do unto you.” Phrased differently around the world, but a universal teaching found in a great many religions and cultures. See, for example, here and here.

“The only definition that can be given of morality is this: That which is selfish is immoral, and that which is unselfish is moral.”

“Let us do good because it is good to do good; he who does good work even in order to get to heaven binds himself down.”

— both quotes from the final chapter of Karma Yoga (pgs. 80 & 86 respectively)

“Replace greed by love, and everything will come right.”

— Young India, Nov. 13, 1924, compiled in The Essential Gandhi pg. 254 or 292 depending on your version of it

For a bit on Gandhi’s relationship to the Bhagavad Gita, and him referring to it as his “spiritual reference book” and “eternal mother” see here

“Whatever you do will be insignificant, but it is very important that you do it. It’s the action, not the fruit of the action, that’s important. You have to do the right thing. It may not be in your power, may not be in your time, that there’ll be any fruit. But that doesn’t mean you stop doing the right thing. You may never know what results come from your action. But if you do nothing, there will be no result. And remember — in doing something, do it with love or never do it at all.”

— See Mahatma Gandhi: On the Wisdom and the Meaning of Life

“This is the way of peace— overcome evil with good, and falsehood with truth, and hatred with love. The Golden Rule would do equally well. There is nothing new about that except the practice of it.”

— Peace Pilgrim: Her Life and Work in Her Own Words, Ch. 3: The Pilgrimage, pg. 26 (2013 edition of originally a 1982 publication)

“Before we go any further I would like to ask you what is your fundamental, lasting interest in life? Putting all oblique answers aside and dealing with this question directly and honestly, what would you answer? Do you know?

Isn't it yourself? Anyway, that is what most of us would say if we answered truthfully. I am interested in my progress, my job, my family, the little corner in which I live, in getting a better position for myself, more prestige, more power, more domination over others and so on. I think it would be logical, wouldn't it, to admit to ourselves that that is what most of us are primarily interested in - 'me' first?

Some of us would say that it is wrong to be primarily interested in ourselves. But what is wrong about it except that we seldom decently, honestly, admit it? If we do, we are rather ashamed of it. So there it is - one is fundamentally interested in oneself, and for various ideological or traditional reasons one thinks it is wrong. But what one thinks is irrelevant. Why introduce the factor of its being wrong? That is an idea, a concept. What is a fact is that one is fundamentally and lastingly interested in oneself.

You may say that it is more satisfactory to help another than to think about yourself. What is the difference? It is still self-concern. If it gives you greater satisfaction to help others, you are concerned about what will give you greater satisfaction. Why bring any ideological concept into it? Why this double thinking? Why not say, `What I really want is satisfaction, whether in sex, or in helping others, or in becoming a great saint, scientist or politician'?

It is the same process, isn't it? Satisfaction in all sorts of ways, subtle and obvious, is what we want. When we say we want freedom we want it because we think it may be wonderfully satisfying, and the ultimate satisfaction, of course, is this peculiar idea of self-realization. What we are really seeking is a satisfaction in which there is no dissatisfaction at all.”

— Freedom from the Known, beginning of chapter 5

“Where creature stops, God begins to be. Now all God wants of you is for you to go out of yourself in the way of creatureliness and let God be within you. The least creaturely image that takes shape in you is as big as God. How is that? It deprives you of the whole of God. As soon as this image comes in, God has to leave with all His Godhead. But when the image goes out, God comes in. God desires you to go out of yourself (as creature) as much as if all His blessedness depended on it. My dear friend, what harm can it do you to do God the favor of letting Him be God in you? Go right out of yourself for God's sake, and God will go right out of Himself for your sake! When these two have gone out, what is left is one and simple.”

— pg. 110 of The Complete Mystical Works of Meister Eckhart, translated and edited by Maurice O'C. Walshe, Revised with a Foreword by Bernard McGinn - 2007; a condensed reissue of a three-volume work released in 1979

“If I am empty, God of his very nature is obliged to give himself to me to fill me … What does emptiness mean? It means a turning from creatures: the heart uplifted to … God, the perfect good.”

— saying 10 of Meister Eckhart, from Whom God Hid Nothing: Sermons, Writings, and Sayings

“The element of truth behind all this, which people are so ready to disavow, is that [humans] are not gentle creatures who want to be loved, and who at the most can defend themselves if attacked; they are, on the contrary, creatures among whose instinctual endowments is to be reckoned a powerful share of aggressiveness. As a result, their neighbor is for them not only a potential helper or sexual object, but also someone who tempts them to satisfy their aggressiveness on him, to exploit his capacity for work without compensation, to use him sexually without his consent, to seize his possessions, to humiliate him, to cause him pain, to torture and to kill him … Who, in the face of all his experience of life and of history, will have the courage to dispute this assertion?”

— Civilization and its Discontents, pgs. 77-78, Translated by David McLintock, (2004 Penguin Books edition, first published in 1930)

“These dispositions, so ordinary that they almost pass unnoticed, were named by our blunt forefathers the Seven Deadly Sins of pride, anger, envy, avarice, sloth, gluttony and lust. Perhaps you would rather call them — as indeed they are — the seven common forms of egotism. They represent the natural reactions to life of the self-centered human consciousness, enslaved by the “world of multiplicity,” and constitute absolute barriers to its attainment of Reality. So long as these dispositions govern character we can never see or feel things as they are; but only as they affect ourselves, our family, our party, our business, our church, our empire — the I, the Me, the Mine …”

— Practical Mysticism: A Little Book for Normal People, pg. 58

“The ego … is one’s biological inheritance, and without it, nobody would be alive to lament its limitations. By understanding its origin and intrinsic importance to survival, the ego can be seen as being of great benefit but prone to becoming unruly and causing emotional, psychological, and spiritual problems if not resolved or transcended … Animal life had to acquire what was needed from its environment, and that principle then established the main core of the ego, which is still primarily involved in self-interest, acquisition, conquering, and rivalry with other organisms for survival. Importantly, however, it also had the characteristics of curiosity, searching, and therefore, learning.

As evolution progressed, the survival mechanisms became more elaborate as the quality of intelligence, by which information is acquired, stored, processed, compared, integrated, correlated, and stratified … Life then evolved into progressively higher life forms. [At its base level] life could be described as rapacious. It acquires its energy at the expense of others, and because survival is based on acquisition, it sees others as rivals, competitors, and enemies. [At that level], therefore, [it] is strongly rivalrous and self-interested. [However, in its higher expression] life becomes more harmonious. Maternal caring appears, along with concern for others, pack loyalty, identification with others, and the beginning of what is later expressed in human nature as relatedness, socializing, play, family and pair bonding, and group cooperation for shared goals, such as survival via community activities …

The persistence of the primitive ego in man is referred to as the narcissistic core of ‘egotism’, which … indicates the presence of the primitivenes of self-interest, disregard for the rights of others, and seeing others as enemies and competitors rather than as allies.

[As we evolve] the brain’s physiology also changes dramatically … from predatory to benign. This is expressed by the emergence of concern for the welfare, survival, and happiness of others rather than just for the personal self.”

— Transcending the Levels of Consciousness: The Stairway to Enlightenment, a bit of a mashup of the Overview section, pgs. 25-31

“It is the motive that establishes spiritual value. To dedicate one’s actions as a service of love to life is to sanctify them and transform them from self-seeking motives to unselfish gifts.”

— The Eye of the I From Which Nothing is Hidden pg. 69

“Swami Sivananda was born on September 8, 1887, to a well known and respected family in Tamil Nadu, South India. As a young boy he already showed spiritual tendencies, then as a young man he felt the strong urge to work in the service of humanity. For this reason, he became a medical doctor and served the poor in Malaysia for several years. He also wrote and published a health journal to spread helpful information on health and hygiene. Later he came to realize that medicine alone could not alleviate the deep suffering of humanity, and that a more profound approach to healing would be needed.

Driven by his wish to find the deeper causes of people’s suffering, and the way to alleviate it, he gave up his medical career and entered into a life of renunciation. He returned to India and spent a year traveling before settling in Rishikesh, in the Himalayas, in 1924. In Rishikesh he practiced intense austerities, and met his guru, Swami Vishwananda. He was initiated into sannyas (monkhood), and given the name Swami Sivananda Saraswati.”

— Sivananda Ashram Yoga Farm biography of Swami Sivananda

“What is the object in … service? Why do you serve poor people and the suffering humanity at large? Why do you serve the society and the country?

By doing service, you purify your heart. Egoism, hatred, jealousy, idea of superiority vanish. Humility, pure love, sympathy, tolerance, and mercy are developed. Sense of separateness is annihilated. Selfishness is eradicated. You get a broad outlook of life. You begin to feel oneness or unity of life. You develop a broad heart with broad, generous views. Eventually, you get Knowledge of the Self. You realise the 'One-in-all' and 'all-in-One'. You feel unbounded joy.

The first step in the spiritual path is selfless service of humanity. Selfless service is the watchword along the road to salvation. Selfless service of humanity prepares the aspirant for the attainment of cosmic consciousness, or the life of oneness or unity with God. Aspirants should direct their whole attention in the beginning towards removal of selfishness by protracted selfless service.”

— Swami Sivananda on Selfless Service

“You are the architect of your own fate. You are the master of your own destiny. You can do and undo things. You sow an action and reap a tendency. You sow a tendency and reap a habit. You sow a habit and reap your character. You sow your character and reap your destiny. Therefore, destiny is your own creation. You can undo it if you like – destiny is a bundle of habits.”

— See here

“You have the right to work, but never to the fruit of work. You should never engage in action for the sake of reward, nor should you long for inaction.”

— Chapter 2 Verse 47 as translated by Eknath Easwaran

“We have often heard that the opposite of love is hate. But perhaps the opposite of love is really selfishness, each one caring only for who they consider themselves to be. This self-centeredness is characteristic of ego, and it is what satsang addresses. The greatest opportunity is for human beings to become aware of themselves as consciousness, as so many have done before us.”

— Vaster than Sky, Greater than Space pg. 228

“Everything is yours, but on one infinitely important condition: that it is all given.”

— New Seeds of Contemplation pg. 229

“Man in the world of action loses his centering in the principle of eternity if he is anxious for the outcome of his deeds, but resting them and their fruits on the knees of the Living God he is released by them, as by a sacrifice, from the bondages of the sea of death.”

— The Hero with a Thousand Faces pg. 239

“Try to work selflessly with love. Pour yourself into whatever you do. Then you will feel and experience beauty and love in every field of work. Love and beauty are within you. Try to express them through your actions and you will definitely touch the very source of bliss … By helping others we are, in fact, helping ourselves. On the other hand, every time we do a selfish action, we are harming ourselves …

… Action performed with a spirit of selflessness is far superior to action performed with selfish motives. A person who is inspired by the ideal of selflessness is less attached to the action and more dedicated to the ideal of selflessness. This attitude of selflessness has a beauty of its own. As you feel the bliss and joy of selfless action more and more, you enter deeper and deeper into a state of selflessness and meditation. So in the beginning, just feel inspired by that very ideal. Love the ideal; be inspired by it. In the beginning it is a conscious and deliberate attempt. As you feel more and more inspired by the ideal of selflessness, you start working from your heart. By the very performance of the work, a joy will spring forth from deep within you. Eventually it will become spontaneous …

… Selflessness is all you should ever wish for … Don’t miss a single opportunity you get to serve others.”

— Amma on Selfless Service, see here

“Feed people, serve people, love everybody, tell the truth.”

— a common refrain of Neem Karoli Baba’s, according to Ram Dass’ writings and lectures. See, for example, here

“Know that when you learn to lose yourself, you will reach the beloved. There is no other secret to be learned, and more than this is not known to me.”

— I first encountered this quote on pg. 61 of Ram Dass’ Be Love Now: The Path of the Heart

“And the same can happen when you perceive visually. You look and you see sense objects in your visual field. Usually the objects, the forms, are all that people see. And the forms draw in your attention completely. Whatever is in your visual field, there’s also the underlying field of alertness in which the visual perception arises. And that is inseparable from the feeling of the aliveness of the inner body: the global alertness. When you live like that, there is now a dimension there that you were not aware of before. You are now aware of the essence of your being, which is the field of Now.”

— The Gateway of Silence from the Gateways to Now audiobook. This ten minute YouTube video gives the practice and instruction in full.