You shall love your neighbor as yourself.
Judaism and Christianity. Bible, Leviticus 19.18
Whatever you wish that men would do to you, do so to them.
Christianity. Bible, Matthew 7.12
Not one of you is a believer until he loves for his brother what he loves for himself.
Islam. Forty Hadith of an-Nawawi 13
A man should wander about treating all creatures as he himself would be treated.
Jainism. Sutrakritanga 1.11.33
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.
Confucianism. Mencius VII.A.4
One should not behave towards others in a way which is disagreeable to oneself. This is the essence of morality. All other activities are due to selfish desire.
Hinduism. Mahabharata, Anusasana Parva 113.8
Tsekung 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 do to others what you do not want them to do to you."
Confucianism. Analects 15.23
Comparing oneself to others in such terms as "Just as I am so are they, just as they are so am I," he should neither kill nor cause others to kill.
Buddhism. Sutta Nipata 705
One going to take a pointed stick to pinch a baby bird should first try it on himself to feel how it hurts.
African Traditional Religions. Yoruba Proverb (Nigeria)
One who you think should be hit is none else but you. One who you think should be governed is none else but you. One who you think should be tortured is none else but you. One who you think should be enslaved is none else but you. One who you think should be killed is none else but you. A sage is ingenuous and leads his life after comprehending the parity of the killed and the killer. Therefore, neither does he cause violence to others nor does he make others do so.
Jainism. Acarangasutra 5.101-2
A certain heathen came to Shammai and said to him, "Make me a proselyte, on condition that you teach me the whole Torah while I stand on one foot." Thereupon he repulsed him with the rod which was in his hand. When he went to Hillel, he said to him, "What is hateful to you, do not do to your neighbor: that is the whole Torah; all the rest of it is commentary; go and learn."
Judaism. Talmud, Shabbat 31a