The Golden Rule is universal and common within at least 21 ancient and contemporary faith and religious practices.

Bahá'í World Faith:
"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

Brahmanism:
"This is the sum of Dharma [duty]: Do naught unto others which would cause you pain if done to you". Mahabharata, 5:1517 "

Buddhism:
"...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

Christianity:
"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." 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.
"...and don't do what you hate...", Gospel of Thomas 6. The Gospel of Thomas is one of about 40 gospels that were widely accepted among early Christians, but which never made it into the Christian Scriptures (New Testament).

Confucianism:
"Do not do to others what you do not want them to do to you" Analects 15:23
"Tse-kung asked, 'Is there one word that can serve as a principle of conduct for life?' Confucius replied, 'It is the word 'shu' -- reciprocity. Do not impose on others what you yourself do not desire.'" Doctrine of the Mean 13.3
"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

Ancient Egyptian:
"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.

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

Humanism:
"(5) Humanists acknowledge human interdependence, the need for mutual respect and the kinship of all humanity."
"(11) Humanists affirm that individual and social problems can only be resolved by means of human reason, intelligent effort, critical thinking joined with compassion and a spirit of empathy for all living beings. " 4
"Don't do things you wouldn't want to have done to you, British Humanist Society. 3

Islam:
"None of you [truly] believes until he wishes for his brother what he wishes for himself." Number 13 of Imam "Al-Nawawi's Forty Hadiths." 5

Jainism:
"Therefore, neither does he [a sage] cause violence to others nor does he make others do so." Acarangasutra 5.101-2.
"In happiness and suffering, in joy and grief, we should regard all creatures as we regard our own self." Lord Mahavira, 24th Tirthankara
"A man should wander about treating all creatures as he himself would be treated. "Sutrakritanga 1.11.33

Judaism:
"...thou shalt love thy neighbor as thyself.", Leviticus 19:18
"What is hateful to you, do not to your fellow man. This is the law: all the rest is commentary." Talmud, Shabbat 31a.
"And what you hate, do not do to any one." Tobit 4:15 6

Native American Spirituality:
"Respect for all life is the foundation." The Great Law of Peace.
"All things are our relatives; what we do to everything, we do to ourselves. All is really One." Black Elk
"Do not wrong or hate your neighbor. For it is not he who you wrong, but yourself." Pima proverb.

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

Shinto:
"The heart of the person before you is a mirror. See there your own form"
"Be charitable to all beings, love is the representative of God." Ko-ji-ki Hachiman Kasuga

Sikhism:
"Compassion-mercy and religion are the support of the entire world". Japji Sahib
"Don't create enmity with anyone as God is within everyone." Guru Arjan Devji 259
"No one is my enemy, none a stranger and everyone is my friend." Guru Arjan Dev : AG 1299

Sufism:
"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.

Taoism:
"Regard your neighbor's gain as your own gain, and your neighbor's loss as your own loss." T'ai Shang Kan Ying P'ien.

"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

Unitarian:
"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."

Zoroastrianism:
"That nature alone is good which refrains from doing unto another whatsoever is not good for itself". Dadistan-i-dinik 94:5
"Whatever is disagreeable to yourself do not do unto others." Shayast-na-Shayast 13:29