Let no one seek his own good, but the good of his neighbor.

This concept is found in all the major religions of the world. So many differences, yet so many similarities. The problem is convincing people that this rule applies to all, not just those who hold to the same belief.

But I say unto you, Love your enemies, bless them that curse you, do good to them that hate you, and pray for them which despitefully use you, and persecute you; - Matthew 5:44; Luke 6:27

"Ascribe not to any soul that which thou wouldst not have ascribed to thee, and say not that which thou doest not." "Blessed is he who preferreth his brother before himself." Baha'u'llah

"And if thine eyes be turned towards justice, choose thou

for thy neighbour that which thou choosest for thyself." Epistle to the Son of the Wolf

"...a state that is not pleasing or delightful to me, how could I inflict that upon another?" Samyutta NIkaya v. 353 

Hurt not others in ways that you yourself would find hurtful." Udana-Varga 5:18

Hurt not others in ways that you yourself would find hurtful.  -Udana-Varga, 5:18

"Therefore all things whatsoever ye would that men should do to you, do ye even so to them: for this is the law and the prophets." -Yahshua Matthew 7:12, King James Version.

And as ye would that men should do to you, do ye also to them likewise." Luke 6:31, King James Version.

"Try your best to treat others as you would wish to be treated yourself, and you will find that this is the shortest way to benevolence." Mencius VII.A.4

"Do for one who may do for you, that you may cause him thus to do." The Tale of the Eloquent Peasant, 109 - 110 Translated by R.B. Parkinson. The original dates to 1970 to 1640 BCE and may be the earliest version ever written.

"One should not behave towards others in a way which is disagreeable to oneself." Mencius Vii.A.4 

"...critical intelligence, infused by a sense of human caring, is the best method that humanity has for resolving problems. Reason should be balanced with compassion and empathy and the whole person fulfilled." Humanist Manifesto II; Ethics section.

No one of you is a believer until he desires for his brother that which he desires for himself. -Sunnab; Number 13 of Imam "Al-Nawawi's Forty Hadiths.

"Therefore, neither does he [a sage] cause violence to others nor does he make others do so." Acarangasutra 5.101-2. 

"A man should wander about treating all creatures as he himself would be treated. "Sutrakritanga 1.11.33

"And what you hate, do not do to any one." Tobit 4:15

"All things are our relatives; what we do to everything, we do to ourselves. All is really One." Black Elk

Roman Pagan Religion

"The law imprinted on the hearts of all men is to love the members of society as themselves."

"20: Try to treat others as you would want them to treat you." This is one of the 21 moral precepts that form the moral code explained in L. Ron Hubbard's booklet "The Way to Happiness."

Sikhism

Compassion-mercy and religion are the support of the entire world". Japji Sahib

"No one is my enemy, none a stranger and everyone is my friend." Guru Arjan Dev : AG 1299

"The basis of Sufism is consideration of the hearts and feelings of others. If you haven't the will to gladden someone's heart, then at least beware lest you hurt someone's heart, for on our path, no sin exists but this." Dr. Javad Nurbakhsh, Master of the Nimatullahi Sufi Order.

"The sage has no interest of his own, but takes the interests of the people as his own. He is kind to the kind; he is also kind to the unkind: for Virtue is kind. He is faithful to the faithful; he is also faithful to the unfaithful: for Virtue is faithful." Tao Teh Ching, Chapter 49

"We affirm and promote respect for the interdependent of all existence of which we are a part." Unitarian principles.

Wicca:

"An it harm no one, do what thou wilt" (i.e. do what ever you will, as long as it harms nobody, including yourself). One's will is to be carefully thought out in advance of action. This is called the Wiccan Rede

Yoruba (Nigeria)

"One going to take a pointed stick to pinch a baby bird should first try it on himself to feel how it hurts."

"Whatever is disagreeable to yourself do not do unto others."  Shayast-na-Shayast 13:29

What you would avoid suffering yourself, seek not to impose on others." (circa 100 CE) - Epictetus

"May I do to others as I would that they should do unto me." (Greece; 4^th century BCE) - Plato

"Do not do to others that which would anger you if others did it to you." (Greece; 5^th century BCE) - Socrates

"Treat your inferiors as you would be treated by your superiors," Epistle 47:11 (Rome; 1^st century CE) - Seneca

http://www.teaching-values.com/goldenrule.html